tag:blogger.com,1999:blog-39336196786966604472024-02-02T09:37:51.643+00:00Electronics Design BlogAn electronics design blog for professional and amateur engineers, technicians, hackers, experimenters. Highlighting my own projects, but also taking a look at the electronics world in general.Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.comBlogger39125tag:blogger.com,1999:blog-3933619678696660447.post-4127438015816160942013-02-12T04:28:00.001+00:002013-02-12T04:28:49.848+00:00So, What Does 2013 Have In Store?<span style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: small;">We are now well into 2013, and the Chinese New Year holiday has just started. Anyone involved with commercial electronics will know what an inconvenience that can be, but if anyone deserves a holiday, it is the Chinese workers! I for one am not going to begrudge them some time off to see their loved ones. This seems like a good time to take stock of what has happened since my last post, and what my intentions are for 2013.</span></span><br />
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<b><span style="font-size: large;"><span style="font-family: Arial,Helvetica,sans-serif;">A Sad Goodbye</span></span></b><br />
<span style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: small;"><br /></span></span>
<span style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: small;">As 2012 came to a close, I received some bad news. My good colleague and close personal friend Simon Allen of Intravention Electronics passed away unexpectedly. He was only in his mid 40s, and not much older than me. It takes something like this to make you think about your own mortality, and how fleeting life is. Simon and I had come together when a mutual friend of ours was going through a difficult time. We had known each other for some time, but didn't realise we were in the same business. </span></span><br />
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<span style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: small;">Since then we had worked together on several projects - Simon was a great sounding board for my ideas and an excellent "sanity" checker. When Simon passed away we were working on a couple of commercial products. It is a great sadness to me that Simon took with him so much good humoured knowledge and experience. </span></span><br />
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<span style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: small;">That rather took the wind out of my sails, forcing me to drop a lot of stuff I was working on. Obviously I don't want to go into details here, but I am now considering whether it might not be the right time to move back into permanent employment rather than being a freelance.The recession is dragging on, and life as a freelan<span style="font-size: small;">cer isn't looking too good here.</span></span></span><br />
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<b><span style="font-size: large;"><span style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: large;">Onwards...</span> </span></span></b><br />
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<span style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: small;">Anyway, as t<span style="font-size: small;">hey say, </span>life goes on. I finally got around to buying a new calculator! After writing many words on the subject I finally put my hand in my pocket and bought an HP-35S. I could write an in-depth review about what it does and doesn't do. I don't think I need to though, all I can say is that I wish I had bought one long ago. It doesn't have some of the facilities my old HP-28S has, but in all honesty I can't see myself performing matrix operations on a pocket calculator now. The HP-35S actually looks and feels like an engineering tool rather than a toy. It has enough of the old-school look and feel without being an antique. Perfect.</span></span><br />
<span style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: small;"><br />Part of me still wants a true old-school looking calculator with a nice fast ARM processor and OLED screen though...</span></span><br />
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<span style="font-size: large;"><b><span style="font-family: Arial,Helvetica,sans-serif;">So What About the LCR Meter?</span></b></span><br />
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<span style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: small;">A good question. The design has been through a couple of revisions since I last wrote about it. Expanding the <span style="font-size: small;">current and voltage range of the AD chip I was using has proven quite effective but rather complicated to execute. </span></span></span><br />
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<span style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: small;"><span style="font-size: small;">A thought struck me - if I were designing this on a clea<span style="font-size: small;">n sheet of paper, what would I do? </span></span>After thinking about it, I have gone back to the drawing board. Rather than hack stuff onto the AD5933, how about using an FPGA, with separate AD<span style="font-size: small;">C and </span>DAC? That would allow me to generate higher resolution, allow me much better control over the signal generation and analysis, <span style="font-size: small;">plus it would allow me to configure it as an arbitrar<span style="font-size: small;">y signal generator, plus audio spectrum analyser</span></span>. If you are going to do feature creep, do it properly!</span></span><br />
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<br />Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-87857688554955905312012-10-02T05:32:00.000+01:002012-10-02T05:32:05.077+01:006.002X version 2, and MITx: 6.00x Introduction to Computer Science and Programming<h2>
6.002x Revisited (Briefly)</h2>
My review of MIT's 6.002X electronics course seems to have been well received, and the lectures are is now part-way through their second run-through. I was disappointed to see that not much has changed. The videos are still of generally poor quality and slightly confused.<br />
<br />
There is one change of note though. You may remember that one of my criticisms was in the area of answer entry. You often had to type in a horrible sequence of variables on a single line, which may or may not have resembled your answer. Getting a red cross meant you had to try again, not knowing whether your answer was wrong, or just your data entry. I suggested that the LaTeX formatting engine used in the questions could be used, to display your answer in a clearer format. I am pleased to say they have done exactly that!<br />
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Answers are now converted on-the-fly to a much clearer mathematical expression on the screen. Excellent stuff, and a big green tick for that!<br />
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<h2>
<span class="provider">MITx:</span> 6.00x Introduction to Computer Science and Programming</h2>
It is now a couple of decades since I formally studied Computer Science, so I thought I would stick my head around the metaphorical lecture room door and see what has changed. To be fair, 6.00x has only been running a day, but there are some points worthy of comment. The 6.002x people should sit up and take note.<br />
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Firstly, technical quality. Rather than use a disembodied voice, we get to see the lecturer close-up on screen, with a microphone close by. On some of the videos I saw, the audio bit-rate was highly variable; some were 192kbit/s quality, others were closer to 32kbit/s. For the most part though, he is clearly audible and his presentation has been tailored to a single viewer rather than a full lecture theatre.<br />
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Secondly, the diagrams and so on have been prepared beforehand and are of a very good standard. Unlike the scruffy hand-drawn notes in 6.002x. Using these pre-drawn diagrams probably saves 10-15% of lecture time alone, and smooths the lecture's flow in general.<br />
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One particularly nice touch is the mention of Alan Turing's name. A man who is increasingly seen as the father of computer science, and whose name has been comparatively unknown for too long. <br />
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So far so good, I think I will stick with this one and get to grips with Python.I doubt it will take over from C in my toolkit any time soon, but it is certainly gaining in popularity.<br />
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<br />Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-46783197215980866362012-09-07T18:05:00.003+01:002012-09-07T18:05:27.008+01:00The London Underground Map - as a PCB?<a class="bbc_link" href="http://london-underground.blogspot.co.uk/2012/09/the-tube-map-as-radio-circuit-board.html" target="_blank">http://london-underground.blogspot.co.uk/2012/09/the-tube-map-as-radio-circuit-board.html</a><br /><br /><img alt="" class="bbc_img" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhR8RDA6zrMv_xnE8Wqc1H9I1L4HrErROIxISBX1xk2RbTFCMDOwYDHEUA-cxg81OUxKW0LP1HL8GV-pi-jRd06v1TLN-US3klRx9yqakr_bPmwfIlOsCmW9fMdFaEnL7UBNu1G_tTklQA/s400/map_04.jpg" /><br /><br />How brilliant is that! A working radio, laid out as a real tube map. I bet the stray capacitance is an absolute swine though.<br /><br />The
designer of the original tube map, an engineering draftsman named Harry
Beck, is widely thought to have based the classic London Underground
tube map on electric circuit diagrams. Wiki disagrees, but he was an
engineering draftsman, so must have been at least been heavily influenced
by wiring schematics.<br /><br />The same designer has also done this. Not quite sure what to make of it: <a class="bbc_link" href="http://www.designboom.com/weblog/cat/16/view/23447/yuri-suzuki-technology-will-save-us-denki-puzzle.html" target="_blank">http://www.designboom.com/weblog/cat/16/view/23447/yuri-suzuki-technology-will-save-us-denki-puzzle.html</a>Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-47960352494003546992012-06-20T19:42:00.000+01:002012-06-21T01:20:32.164+01:00MIT 6.002x Circuits & Electronics: Tries Hard, Could Do Better.<br />
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I hope this goes some way to explaining where I have been
for the last few months.</div>
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<b><span style="font-size: large;">MIT 6.002x Circuits and Electronics</span></b></div>
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<a href="https://6002x.mitx.mit.edu/">6.002X</a> is the online version of the respected Massachusetts
Institute of Technology course 6.002 “Circuits and Electronics”. It has just
completed its first run-through, and I have been one of the first "guinea
pig" students taking it.</div>
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<b><span style="font-size: large;">Full Term Report.</span></b></div>
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When I was at school, like most children I used to get
regular school reports sent home to my parents. The first page consisted of
“advice to both parents and teachers” informing them that vague and unhelpful
clichés such as “could do better” or “tries hard” should be not be used and
that parents should be given more useful comments. After working my socks off
and (I thought) doing really rather well in my class, this eleven year-old’s
very first term’s report said:</div>
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<span style="font-size: large;"><i style="font-family: Times,"Times New Roman",serif;">"Tries
hard, could do better."</i></span></div>
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As you will see, it seems appropriate for this course.
However, in an attempt to be less vague and unhelpful, I decided that a blog
was probably the best way to get my opinions and ideas across. </div>
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<span style="font-size: large;"><b>Kindergarten</b></span></div>
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I think I need to offer some context here. My first Degree
is not purely in electronics, but is shared with software engineering and
system development. Despite finding the systems and software aspects both
interesting and useful in my career, as time has gone on I have regretted not
having a deeper understanding of “pure” electronics, but there is only so much
you can fit into 4 years study. So, when the esteemed M.I.T. announced that it
was making one of their electronics courses available as “Open Courseware” then
it seemed the perfect match for my needs. A good time to brush up on forgotten
facts, and learn some new ones too.</div>
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I had already watched most of the recorded <a href="http://www.youtube.com/watch?v=AfQxyVuLeCs">6.002 “live”(i.e. recorded in a lecture theatre) lectures</a> on YouTube and they seemed okay.
No better than that though, and certainly not up to the quality of W<a href="http://www.youtube.com/watch?v=PmJV8CHIqFc">alterLewin’s MITphysics lectures</a>. Given the
prestigious name of the institution and their reputation for ground-breaking
methods developed in the Media Lab, my expectation was that, as part of the
transition to on-line delivery, they would have taken time to prepare a clear
and thorough presentation of the subject, taking academic lectures to a whole
new level.</div>
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<span style="font-size: large;"><b>Open Courseware is Nothing New!</b></span></div>
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<a href="http://hub.tv-ark.org.uk/images/schoolstv/bbc_education/bbc_ou/the_open_university_060780b-small.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" src="http://hub.tv-ark.org.uk/images/schoolstv/bbc_education/bbc_ou/the_open_university_060780b-small.jpg" /></a>Here in the UK, we have an institution called <a href="http://www.open.ac.uk/">The Open University</a>.
It was founded by the government in 1969 as "the university of the air" with the aim of making high quality
higher education available to everyone. One of the unique aspects of the O.U.
was the use of <a href="http://www.youtube.com/watch?v=3JbV6llUJd8">broadcast television in order to distribute lectures</a> – remember
that in the 1960s and 70s virtually nobody had a video recorder.</div>
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Sadly, as time went on, the O.U. realised it could
distribute lectures on VHS cassette, then DVD, with the result that by 2000
virtually no academic programmes were being broadcast on free-to-air, just the
“fluffy” populist programmes with little academic rigour. I would really like
to see the O.U.'s back-catalogue of lectures available free on YouTube or
similar service. The technical quality may not be great (heck, many of them are
in black and white) but the content is exceptional.</div>
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I may be an engineer by profession, but I grew up in the
70s, 80s (and 90s) watching low budget but well designed programmes, not just
ones on physics and mathematics, but history, chemistry, art, languages,
literature… You get the idea. Lots of things. I didn’t understand all of it by
any means, but I feel it made me a better person, and it instilled in me a
hunger to learn. Free, high quality education changes lives for the better.
Even, or perhaps especially, the less advantaged parts of the world.</div>
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If I seem critical of 6.002x in this report, then it is from
a desire to see it work, and work well, and to foster the development of much
more open courseware. I know what effect the O.U. had, and the thought of what
MIT (together with Harvard, Stanford and the like) can achieve with MITx is one
of the most exciting things I have seen in a long time. It really does need
more work though. So, here we go. The criticism.</div>
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<span style="font-size: large;"><b>Presentation</b></span></div>
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Professor Agarwal is to be lauded for his work in making
this course available to the entire world, and I think his enthusiasm makes him
the ideal person to spearhead the open courseware movement. I have to be honest
though, and admit that his presentation style is not ideal in this particular context.
Note that I am not talking about his accent, although I can see how people
whose first language is not English may well be confused.</div>
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When I was at university (which to my horror I have realised
is now nearly 20 years ago and thus several generations in technology terms)
the lecturers would often use pre-prepared overhead projector (OHP) slides with
spaces to work through problems. This produced a nice linear work-flow which
made it easy to write clear and effective notes. The slides themselves were
also available later as photocopies for students who had been unable to attend
the lecture. I found it worked very well indeed both for learning and revision.
Think of it, if you will, as pre-written blackboards. The lecturer doesn't need
to spend time writing things down, so you can get on with the business of
actually learning.</div>
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The existing real-world 6.002 lectures take place in a
multi-hundred seat lecture theatre, with a conventional blackboard (chalk-board
to all the non-native English speakers). This retains some linearity but can
get messy, and the lecturer spends a considerable amount of time simply
s-l-o-w-l-y writing things down. A phrase which takes two seconds to say and
understand can take ten seconds to write.</div>
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However, rather than repeat the existing video lectures, MIT
have taken the decision to go with virtual slides; basically Dr Agarwal writing
on a screen via a graphics tablet. As you can imagine, each slide can get
rather cluttered and confused by the end of each lecture video. The flow,
rather than being in a linear sequence, is <a href="https://www.youtube.com/watch?v=ri5VFFjuSQI">all over the place and useless forrevision</a>.</div>
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<a href="http://i222.photobucket.com/albums/dd237/Zadpics/6002x-example.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="224" src="http://i222.photobucket.com/albums/dd237/Zadpics/6002x-example.png" width="400" /></a></div>
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The move to a web-delivered format should, in theory, enable
a more carefully crafted and controlled learning experience with a good flow
and clear graphics and animations. Instead, we have the lecturer writing on a
graphics tablet, over a tiny area. This is exactly the same content seen on the
black/whiteboard in the live lectures. The tiny area makes things get cluttered
very quickly indeed, and the thick “pen” used is rather unclear. The resultant
image is crammed into 674x379 pixels, as you can see above.</div>
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I appreciate that using a small screen size allows lectures
to be viewed on small hand-held devices, but it compromises the delivery of
those lectures, and at this stage we should not be looking at the lowest common
denominator but, instead, how current technologies might be used to improve the
presentation.</div>
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I’m afraid the lectures have the feeling of “oh bugger, I
forgot to prepare anything, I will do it as I go along”. You can get away with
this in real lectures, but for video presentation then I’m afraid it isn’t good
enough.</div>
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The very first presentation I gave in front of an audience
at university was hacked together in a couple of hours the night before, and I
hand-wrote many of the slides as I went along. I got a C grade for doing
enough, but the other students showed me that I should have prepared far better
than I had. These lectures have a similar feel to mine.</div>
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With all the resources of MIT, it must surely be possible
for someone to digest these lectures and present them in the form of mostly
pre-made slides? Some of the slides we see are partly pre-drawn, but get
cluttered very quickly (see above) and Prof. Agarwal has a habit of adding
unnecessary “fluff” and comments.</div>
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The original 6.002 lectures are recorded in a live lecture
theatre, the sound is generally crisp and consistent. I wish I could say the
same for the 6.002x version. Not only is the sound frequently muffled and
masked with rustling, but the audio levels vary massively, even within one
5-minute video. It is clear that they weren't being monitored during recording,
or even reviewed afterwards.</div>
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<span style="font-size: large;"><b>(Not) Recorded In Front of A Live Audience</b></span></div>
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I have just been watching an interview with the instructors
( https://6002x.mitx.mit.edu/section/instructor_interview/ ) and they raise
some relevant points which are largely unanswered among the “didn’t we do well”
mutual back-slapping. The main one is the important role that feedback plays in
lectures. Students point out mistakes, and a puzzled expression on several
faces can tell the instructor that their explanation is unclear, and thus
should perhaps be trying an alternative approach. This is never going to happen
when recording in a booth with a monitor and graphics tablet for company.</div>
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I'm afraid that Prof Agarwal gets into the habit of repeating
himself quite a lot. By the final lectures he was saying the same thing as many
as four times. This is annoying, wastes time, and breaks up the train of
thought. It could (and should) have been edited out. Recaps at the start of
every section just aren't needed when the student can click a button and see
the previous sub-lecture. When you are watching a sequence of lectures, it gets
really irritating to have a recap every 5 to 10 minutes.</div>
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<span style="font-size: large;"><b>Rate of Delivery</b></span></div>
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In the official introduction, we are told that we should be
spending around ten hours a week on 6.002x, including lectures, tutorials, lab
work and homework. To do justice to the subject, ten hours is probably somewhat
on the low side, especially if you are returning to formal education after
years away and need to do some catch-up work on the maths or whatever
(remember: you can't pause the course to revise another subject). At over 1000
pages, the course text book would take well over 10 hours a week to complete,
even if you were only doing a few of the exercises.</div>
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That doesn’t seem too bad does it, ten hours in a whole
week. Let me put it another way though. That is 25% of a full time job, or 1.5
hours every day. Let us assume that we
are unable to study one day. This means that we need to find three hours study
time the next day in order to catch up. Sadly, real world events happen and
these hours mount up, and it is horribly easy to get left behind. The chain
nature of the subject means that it is difficult to cut your losses and start a
new subject. The result is that it becomes impossible to catch up.
Unfortunately, this is what happened to me when a family member became ill.
This is always going to happen in the "real" world, more so than among
a group of full-time students without young (or elderly) families to look
after.</div>
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Rather than having two lectures per week and running for 13
weeks, I would run it at half that speed. Better still, why not have it
on-demand? If the need for regular testing is removed (see later in this blog
post) then I see no reason why a student could not progress at their own rate,
and do full justice to the subject, instead of having to gloss over parts
because of time restrictions. Mid- and end-of-term testing could still happen
at fixed quarterly intervals, with the student undertaking them only when they
felt confident to do so.</div>
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<span style="font-size: large;"><b>Testing, Testing, 1... 2...</b></span></div>
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Currently, testing is in two formats. Firstly, each week has
a set homework which must be completed within 2 weeks of being set. Labs are
effectively a second homework, with the same issue and completion dates. So far as I can see, there little policing of
homework answers on the official forum, and other web sites also contain discussion
about homework, with extensive worked answers for most of the questions. </div>
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It is perfectly possible for a student with no electrical
knowledge (but a whizz on Google) to be able to find the homework answers and
copy them over. In fact, most discussion seems to be along the lines of “I need
the answer to Hw7 Question 3”. The on-line chatter about 6.002x definitely has
the emphasis on passing tests rather than understanding the subject. I am aware
that there are groups of students out there who share sets of answers. The
result of this is going to be a set of students who know nothing about
engineering but who have an A grade in an MIT course. This utterly devalues the
brand, and is something MIT need to be aware of.</div>
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I think running the course asynchronously would help reduce
this reliance on copying, but I am afraid that it is going to be endemic in any
system like this, which relies on automated pattern matching rather than a
human being interpreting the submission.</div>
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I guess I was spoiled as a student. The emphasis was very
much on understanding how to solve problems. So, if you got the numerical
result incorrect, or made a mistake in one step along the way, you would still
get the majority of the marks. An engineer is someone who can tell you why
something works, and this testing system just doesn’t support that ethos. All
it wants is a number, or a line of preformatted mathematical text.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Talking of which, the method of submitting expressions is
horrible. The question setters do their best to allow for some flexibility, but
the software cannot take individual style into account when checking an answer,
whereas a human would not see it as an issue at all. I think it was week 5 or
6, which involved extracting MOSFET parameters via calculus. This resulted in a
horrendously complex expression entered as a line of text, which I must have
tried to enter a couple of dozen times before giving up (my calculation was
actually correct). The LaTeX mark-up language is supported in the labs, I don't
see why the homework system shouldn't support it too. Ideally the student could
write the answer (and intermediate steps) in longhand on paper, but this would
obviously not be machine-readable.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
I noticed an excellent article on the BBC Education site
concerning this issue. MITx (and EDx) seem to be looking at a form of
peer-evaluation. This is an excellent idea if correctly carried out. Quite how
they are going to trust a set of random (and inherently uneducated and
inexperienced) individuals to score a paper, I am not quite sure. It definitely
has potential though.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Because of commitments, I was unable to take either
examination. I have heard several comments that people were surprised how easy
it was in comparison to previously published examples. </div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span style="font-size: large;"><b>Labs</b></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
All labs are based around a simplified web-embedded PSPICE
client. This is good so far as it goes, but I was disappointed that an
engineering course lab didn’t have a physical aspect to it. I understand that
this would incur a potential cost on the part of the students, but I believe
this could be done inexpensively with a cheap breadboard and a small collection
of components. It need not be compulsory, but I am sure many students would
welcome the opportunity to understand electronics at a more physical level.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Either way, I would love to see more labs, whether virtual
or physical. Getting a real feel for how components work is vital for any
engineer. Just knowing that an Amp or a Volt is “so much” and “that much makes
a wire melt”. Too many paper engineers don’t have this sense of what is real.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span style="font-size: large;"><b>Tutorials</b></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Each weeks' lectures are accompanied by a small number of
recorded video tutorials. These may cover content from the lectures, or related
skills such as soldering. (Memo to Americans recording electronics videos: You
know how you laugh when we call a cigarette a fag? Well we do the same when you
pronounce soldering as soddering)</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
More tutorials please! These are the strongest part of the
course at the moment. If you want to see how they might be improved, go and
watch some of <a href="http://www.youtube.com/playlist?list=PL3C5D963B695411B6&feature=plcp">Dave Jones' EEVBlog tutorial videos on YouTube.</a></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span style="font-size: large;"><b>Course Text</b></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The course set text is “Foundations of Analog and Digital
Electronic Circuits” by the lecturer (Anant Agarwal) and Jeffrey Lang . At 1008
pages it is certainly no lightweight book. It currently retails for £66 here in
the UK, excluding postage (approximately £3). That is US$107. Yeah.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
To be fair, the entire book has been scanned in and is
available online on the 6.002x web site. You may be one of the fortunate souls
who can read books online with no problem, sadly I am not one of those people,
and printing 1008 pages doesn’t really appeal to me. </div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
If the book weren't the official course text then I wouldn't
look at it twice. There are many better books out there, which present the
subject in a clearer and more methodical manner. I would go as far as to say
that basing the course on this book is holding it back.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span style="font-size: large;"><b>The Emperor’s New Clothes and Education by Omission</b></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
I have seen various comments on web forums concerning
6.002x. Inherently, many are from students who were, for one reason or another,
unable to attend a “real” university. There is a certain amount of comment that
the lectures only cover a small proportion of the subject content. Quite often,
the response to their concerns it “it is MIT, one of the best engineering schools
in the world, of course it is difficult” or “the lectures give you the basic
tools, you are expected to do the rest”.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
</div>
<div class="MsoNormal">
There is a certain amount of validity in this, where the
student is physically within the learning environment. In this case, however,
this approach simply isn't sufficient.Why not just buy the book and work
through the tutorials? 6.002x is no longer a physical university course where
students have multiple sources of support, and the existing lectures do not
provide sufficient information.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
A few weeks ago, I was watching the excellent “Ask
AnEngineer” live Internet video programme, where (MIT alumnus) Limor Fried was
talking to (fellow MIT alumnus) Amanda Wozniak. Someone asked what they thought
of 6.002x. They both expressed surprise that MIT had chosen this particular
module as the first to be trialled. Amanda said she had nearly abandoned the
module half way through, as the maths was becoming overwhelming, and she was
really struggling. I have to say that I have a lot of respect for Amanda as an
engineer, she really knows her beans, and if she was struggling then heaven
help the rest of us.The maths rather overwhelmed me at the same point.</div>
<div class="MsoNormal">
</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
You can call stuff “a bunch of fun” as much as you like (and
Prof Agarwal never shies away from doing so) but hard work is hard work and
should be treated as such. If a student thinks they should be enjoying it and
are simply finding it impossible, then they may well quit. Engineering is hard.
Sure, it can be presented well, and explained from various perspectives, but
there is a lot to learn and no amount of "hey wow guys ain't this
cool" is going to make it quick and easy.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span style="font-size: large;"><b>So... Tries hard. Could do better. But How?</b></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
I am not egotistical enough to assume that MIT give a rat’s
arse about my opinion, but I do think they will pay attention to the general
consensus. I also think that if nobody says anything then they will assume the
course as it stands is perfectly fine and will continue with it in the same
format. It is a good start, for sure, but it isn't fine. 4/10 at most.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span style="font-size: large;">Overall structure.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<ul>
<li>Remove the examinations (for reasons of mass-cheating
mentioned above). Without having a real physically moderated examination, where
the student is required to attend a controlled environment, I think they are
ineffective and serve only to devalue the course, and MIT’s qualifications as a
whole. </li>
</ul>
</div>
<div class="MsoNormal">
</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<ul>
<li>This can be balanced by having more coursework. The only
“qualification” on offer should be a certificate stating that the student has
attended all the lectures and passed the homeworks.</li>
</ul>
</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<ul>
<li>Crucially: Deliver the course flexibly and on-demand, with
no time limits. Allow the student to start when they want and to progress at
their own speed.</li>
</ul>
</div>
<div class="MsoNormal">
</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<ul>
<li>More of the excellent tutorials.</li>
</ul>
</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span style="font-size: large;">Technical quality must improve vastly. </span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
</div>
<div class="MsoNormal">
Let me state at the start; Budget is no excuse for poor
quality.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The audio <i>must </i>be clearer and more consistent in volume. If
MIT’s broadcast facility won’t allow you to use their equipment then
inexpensive semi-pro equipment such as the $100 Samson C01U studio microphone
is excellent quality. Software such as Audacity allows the levels to be
normalised within seconds at the click of a mouse. This is supposed to be
professional. If the quality isn’t good enough then re-record it! Choose a good
bit-rate too, there is some awful compression distortion on some parts.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
</div>
<div class="MsoNormal">
I won't even call the existing quality amateurish. If anyone
at MIT wants to see how good lectures and teaching sessions can be, then please
look around YouTube. </div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The method of using a graphics tablet to write on the screen
is horrible. Worse in terms of readability than the live lectures, and very
wasteful of time. Pre-prepare a full set of clear slides at a good resolution.
Having written a book on this subject, a set of slides should not be difficult.
Yes, this takes time and effort. If you want to give a quality educational
course and don't want to do the work, then let someone else do it instead. In
the spirit of Open-ness I am almost inclined to make a set of animated slides
myself, just to show what can be done even with my mediocre skill in
presentations.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
If need be – script it! This is basically a broadcast TV
show now. Ums, errs, aaaahs and repetitions are utterly unprofessional.
Absolutely fine in lectures, but not in this context.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Avoid clichés like the plague (yes I really did say that).
Avoid calling things “a bunch of fun” or “exciting”. Interesting maybe, but not
fun. Remember you are talking (partly) to teenagers who have recently
discovered alcohol, sex and really loud music. Possibly even all three at the
same time. Is power rail bounce or signal reflection really fun? I'm not
getting all Puritan here, it just really annoys me when someone tries to hype
something up which is clearly rather dull.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
UK people will know what I mean when I say it gets a bit
happy-clappy vicar with a guitar and tambourine. the more you try to "get
down with the kids" the further away you push them.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The book. It needs to be available in print form for under
£30. There are on-demand print services (not to mention dubious sources in
China and India) who will print it for a fraction of that, if the will is there
from MIT and the authors.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
There is content missing or lacking in detail, and content
which could more logically be located in a subsequent course. (For instance:
What happened to bipolar transistors?) This must be the only course I know of
which teaches active components before passives. I don't buy the "because
it is MIT then it must be right". My alma-mater has Nobel prizes too, and
they don't teach electronics in this rather muddled order.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Edit and edit again! Edit the script. Edit the videos and
audio.The final few lectures on power rail bounce and signal reflection could
have been edited down to 75% of the time or less, with no loss of content. At
one point, Prof Agarwal said the same thing four times. Yes four times. He said
the same thing four times. Isn't it bloody irritating and a waste of time when
someone says the same thing four times?</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<b><span style="font-size: large;">Conclusion</span></b></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
All good experiment write-ups should have a conclusion, so
here we are.</div>
<div class="MsoNormal">
<br /></div>
<ul>
<li>Was it worth my time? Yes, definitely.</li>
<li>Would I do it again? Not unless the video lecture content is
massively improved.</li>
<li>Would I do another similar online academic course?
Unreservedly yes.</li>
<li>Would I recommend it to someone looking to study
electronics? Maybe. I suspect it would put a lot of people off serious
engineering.</li>
</ul>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
I really enjoyed getting my brain working again, remembering
long forgotten facts and learning a lot of new stuff. I also learned that I have forgotten a
huge amount of maths. It did soak up a huge amount of my spare time though, and only part of that was watching the videos and working on the assignments.<br />
<br />
With the introduction of <a href="http://www.edxonline.org/" target="_blank">edX</a>, which will effectively be covering all the <a href="https://6002x.mitx.mit.edu/" target="_blank">MITx </a>content now, and the promotion of Prof Agarwal, I suspect 6.002x may well change before the next offering. Hopefully this bringing-together of skills and services will raise the quality of content and delivery. <br />
<br /></div>
<div class="MsoNormal">
With such big names getting serious about Open Courseware, this entire field is going to get very big indeed.On a human scale, it is going to have a huge impact. Possibly even bigger than people yet realise.<br />
<br />
<br /></div>Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com5tag:blogger.com,1999:blog-3933619678696660447.post-20075381525406909352012-03-23T04:56:00.000+00:002012-03-23T04:56:52.205+00:00R.I.P. LCD. Hello OLED?Organic LED (OLED) technology is one of those things that seems to have been on the way for years. It was going to replace LCD tech at a sweep, with ultra sharp, high contrast goodness. Like many such things, it never managed to take the world by storm, but it still has it's own advantages and disadvantages. I have kept meaning to investigate OLEDs for a while so (with one eye on the LCR meter project) I finally got my finger out and blagged a <a href="http://uk.farnell.com/densitron" target="_blank">Densitron </a><a href="http://uk.farnell.com/densitron/dd-12864yo-3a/display-oled-128x64-yellow/dp/1498860" target="_blank">DD-12864YO-3A</a> from <a href="http://farnell.com/" target="_blank">Farnell Element-14</a>.<br />
<br />
Yeah, memorable name. You might guess though, that it is 128x64 pixels, and (monochrome) yellow. I'm used to conventional LCD modules, where a 128x64 might be 100x50mm (4in x 2in) and I had read the data sheet, but I don't think I was ready for quite how small this wee beastie is:<br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/OLED-149-8860.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="310" src="http://i222.photobucket.com/albums/dd237/Zadpics/OLED-149-8860.png" width="400" /></a></div><br />
This instantly raises an issue over the form factor. I guess it is technology intended for mobile phones, but for practical hand held test gear I think it is just a bit too small. You can get 256x64 units which are approximately twice the width, but they are twice the price too, and well into the territory of colour LCD with integrated touch panel.<br />
<br />
I had intended to hack this straight into an Arduino or Mbed, and get a quick demo running, but a few things have stopped me. See that connector in the photo above? 24 pins, each half a millimetre apart - clearly influenced by it's mobile phone background. None of this standard 0.1" header LCD here! Even with the matching socket, it really needs a custom PCB to break out the lines. Fear not though, I have a cunning plan, which involves a load of 30AWG (0.4mm) Kynar wire.This alone is going to slow down take-up when it comes to amateur projects and even professional prototyping. Secondly, though, the module is 3.3V only. No 5V here, no sir. A few resistors should sort that problem out, but it all adds up. Having said that, I don't know of any commercial systems that run 5V any more, so it is no big issue for non-Arduino folks.<br />
<br />
One part of the manufacturer's data informs me that I need an externally generated 12V supply, but another part tells me that it can be generated internally. We shall see.<br />
<br />
Looking at the pinouts, it seems like it is an adaptation of the classic HD44780 chip. It isn't. It uses an SSD1305 which does waaaay more than the old chip. Unfortunately this means it takes a lot more driving too. Just booting it up takes a fairly hefty code sequence. The user can elect (by variously grounding 2 pins) to use a classic 8bit 68xx or 80xx parallel protocol or, more interestingly, use 4-wire SPI or 2-wire I2C. If the manufacturers had desired, they could have easily halved the pin-count by going serial only, and removing three "No connection" pins that they insist should be grounded. I'm sure the market for breakout boards with a boost power supply and a level converter is already out there.<br />
<br />
So, this looks like an interesting little adventure. I can think of a few projects where a module like this would be useful, not least my JTAG adaptor. It is definitely the sort of thing I will bear in mind for future designs, possibly filling in for indicator LEDs rather than low current LCD (the OLED unit draws up to 55mA). I hope to have some shots of a demo up soon.<br />
<br />
Thanks go out to <a href="http://farnell.com/" target="_blank">Farnell Element-14</a> for supplying the <a href="http://uk.farnell.com/densitron" target="_blank">Densitron </a><a href="http://uk.farnell.com/densitron/dd-12864yo-3a/display-oled-128x64-yellow/dp/1498860" target="_blank">DD-12864YO-3A</a>.Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-88197662495811491562011-12-14T03:07:00.004+00:002011-12-16T05:20:07.950+00:00Arduino - DIY Electronics for the 21st Century?Over the past year or two, it has felt like you can't turn a page in a tech magazine, or read a web page about electronics without some reference to the Arduino. Somehow it seems to have moved from serious "difficult" electronics, into an everyday commodity.<br />
<br />
Thus far, I had resisted the Arduino's allure. I don't have any experience with Atmega processors, my usual preference is for one of the Microchip PIC families or, if more power is needed, an ARM cored device. But how could I give an opinion without owning one and having a play around with it? I was impatient as usual, and the people at Farnell / Element-14 had one sitting on my desk within 24 hours. Excellent.<br />
<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/ArduinoUno.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="270" src="http://i222.photobucket.com/albums/dd237/Zadpics/ArduinoUno.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/ArduinoUno.jpg">The Arduino Uno</a></td></tr>
</tbody></table><br />
I will go into more details later, but here is a quick rundown.<br />
<br />
The Arduino Uno is a totally open source embedded development board, based around the Atmel Atmega328. Other "flavours" of Arduino are available, usually based around other Atmega chips. Arduino isn't just limited to the hardware, however. It also covers the development environment which, to my mind, is the crucial factor in it's success.<br />
<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/Arduino2.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="337" src="http://i222.photobucket.com/albums/dd237/Zadpics/Arduino2.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Arial,Helvetica,sans-serif;">The Arduino Development Environment <br />
(Click for larger image)</span></td></tr>
</tbody></table><br />
As you can see from the screen grab above, this isn't Microsoft Visual Studio. Thank goodness. Simple and clean with syntax highlighting. <i>This </i>is why Arduino has taken off.<br />
<br />
The Uno itself measures just 53x69mm, and arrives in a simple cardboard box that looks more like a packet of cigarettes or condoms. No. Really. The accompanying leaflet covers the usual legal disclaimers and little more. It would be nice if it said "Congratulations on your new Arduino, now download your free development software from www.arduino.cc" or similar.<br />
<br />
It is powered via the standard USB "B" socket, or via a jack socket. I find it odd that they haven't moved over to a mini or micro USB, but no great shakes. The general standard of construction is solid, as you might expect with a mature product, the CPU being a socketed 28-pin DIP/DIL device. This is so you can remove it after programming, or plug it into a breadboard. Or, I suppose, replace it if you toast it.<br />
<br />
There is a HUGE amount of resources for the Arduino around the Internet. Almost too many. If you are interested in seeing what it can do, and how easy it is to use, then I recommend <a href="http://www.youtube.com/playlist?list=PLA567CE235D39FA84">Jeremy Blum's YouTube series here.</a><br />
<br />
I got mine from <a href="http://www.farnell.com/">Farnell / Element-14</a>, who stock <a href="http://uk.farnell.com/arduino">a range of Arduinos and related gear</a>.<br />
<br />
The Arduino Uno I reviewed is available here <a href="http://uk.farnell.com/arduino/a000046/board-arduino-uno/dp/1848687 ">http://uk.farnell.com/arduino/a000046/board-arduino-uno/dp/1848687</a> <br />
<br />
Arduino's home is at <a href="http://arduino.cc/">arduino.cc</a><br />
<br />
John's Tronix Stuff tutorials <a href="http://tronixstuff.wordpress.com/tutorials/">here.</a><br />
<br />
<br />
Additional: If anyone has any good Arduino tutorial sites they would like me to add, simply add a comment or drop me a line.Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com3tag:blogger.com,1999:blog-3933619678696660447.post-13598715665783270962011-12-07T04:21:00.000+00:002011-12-07T04:21:07.186+00:00Tektronix DMM4020 Bench-top Digital Multi Meter - First Impressions<h5 style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: 18pt;"><strong><span>This is an initial overview of the Tektronix <span><span id="addProduct-IDE4WaFe-linked" style="white-space: nowrap;"><a class="jive-link-product-addtolist" href="" title="View product details"><span class="pf-widget-map pf-product-info-icon"></span></a><a class="jive-link-product pf-embedded-product-link" href="" title="View product details">DMM4020</a> </span></span> Bench-top Digital Multimeter.</span></strong></span></h5><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;">This overview was originally written for Element-14 and is available <a href="http://www.element14.com/community/thread/15382?tstart=0">here. </a> </div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><a href="http://uk.farnell.com/tektronix/dmm4020/multimeter-bench-5-5-digits/dp/1771901" rel="nofollow" target="_blank"><img alt="http://uk.farnell.com/productimages/farnell/standard/1771901-40.jpg" class="jive-image" src="http://uk.farnell.com/productimages/farnell/standard/1771901-40.jpg" /></a></div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><a class="jive-link-external-small" href="http://uk.farnell.com/tektronix/dmm4020/multimeter-bench-5-5-digits/dp/1771901" rel="nofollow" target="_blank">http://uk.farnell.com/tektronix/dmm4020/multimeter-bench-5-5-digits/dp/1771901</a></div><div class="MsoNormal"><a class="jive-link-external-small" href="http://www.tek.com/products/digital-multimeter/dmm4020/" rel="nofollow" target="_blank">http://www.tek.com/products/digital-multimeter/dmm4020/</a></div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><strong>Unit Price: £528.00 </strong></div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><span>I must stress that this is just an initial overview. The <span><span id="addProduct-N5n039IL-linked" style="white-space: nowrap;"><a class="jive-link-product-addtolist" href="" title="View product details"><span class="pf-widget-map pf-product-info-icon"></span></a><a class="jive-link-product pf-embedded-product-link" href="" title="View product details">DMM4020</a> </span></span> is very much a professional piece of test equipment and needs to be used properly in a work context for some time before I can give a thorough in-depth review. Nevertheless, in the short time that I have had it, I have already learned more than enough to give a good overview.</span></div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal">A few month ago, I had considered that a good bench meter should really go on my list of test gear. Less than a week after its arrival, I wonder how on earth I managed without one. After all, hand-held multimeters are really good now and - it has to be said - more than good enough for most work. So why has a bench meter already earned its place in my lab? Read on…</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal">The meter arrived in sturdy double-layer manufacturer’s box measuring 9”x12”x17”. Inside is a pair of vacuum formed foam blocks which sandwich the meter and provided good impact protection on its journey here. It is the sort of packaging that is worth keeping for storage, should you need to move it around or keep it safe.</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><span>Unless you have a huge bench or a permanent place in a rack, then this meter does take up quite a bit of space, being 9 inches wide and 13 inches front-to-back (although it is tiny in comparison to the high end calibration lab stuff). Traditionally though, bench gear like this does appreciate being left switched on permanently, to allow the temperatures to stabilise, minimise thermal cycles and prevent any moisture affecting components as the lab cools down over night. Unfortunately the <span><span id="addProduct-XaL2xL8b-linked" style="white-space: nowrap;"><a class="jive-link-product-addtolist" href="" title="View product details"><span class="pf-widget-map pf-product-info-icon"></span></a><a class="jive-link-product pf-embedded-product-link" href="" title="View product details">DMM4020</a> </span></span> has a fluorescent display, which has a tendency to fade when left on for extended periods (years). I have not yet discovered a way to turn the display off whilst keeping the electronics running. There is a “soft” power button on the front panel which may well perform a similar function. That is definitely something to investigate. Otherwise, though, the VFD is bright, sharp and fast to react, probably better than LCD could give.</span></div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><span>However, this is jumping ahead slightly. The very first thing that I saw – a printed manual. Yes folks, real paper, with print on it. Spiral bound. Hallelujah! Only 26 pages of it are in English (the rest is Japanese and Chinese). It is only a “Safety And Installation” Manual, but it covers the main functions and accuracy tables. The full User Manual is 110 pages but unfortunately only available in PDF format. I will go more into the contents of this manual in the full review. The S&I manual states that power consumption averages 10 Watts, with a maximum of 15 Watts. Each side of the case is plentifully supplied with ventilation holes, and having left the <span><span id="addProduct-94xBNQzO-linked" style="white-space: nowrap;"><a class="jive-link-product-addtolist" href="" title="View product details"><span class="pf-widget-map pf-product-info-icon"></span></a><a class="jive-link-product pf-embedded-product-link" href="" title="View product details">DMM4020</a> </span></span> on for 6 hours, the temperature stabilised just above ambient. It runs very cool indeed for mains powered gear.</span></div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
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</div><div class="MsoNormal"><span style="font-size: 14pt;"><strong style="mso-bidi-font-weight: normal;">Caution!</strong></span></div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;"><br />
</strong></div><div class="MsoNormal"><span>There are two things to watch out for before you start. Most importantly, the <span><span id="addProduct-7L2T17JU-linked" style="white-space: nowrap;"><a class="jive-link-product-addtolist" href="" title="View product details"><span class="pf-widget-map pf-product-info-icon"></span></a><a class="jive-link-product pf-embedded-product-link" href="" title="View product details">DMM4020</a> </span></span> uses a conventional transformer power supply </span><span style="color: red;">which is supplied configured for 110V</span>.</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal">It takes until page 10 of the Installation Guide before it mentions line voltage selection. I imagine almost all users will know to check this first, but in a world where people are increasingly used to switched mode power supplies that take 100-240V without configuration, a caution sticker would probably be wise. The actual method of voltage selection is a bit odd but nevertheless functional; You unclip and remove a module which has the mains fuse and a plastic “spider” inside, which is rotated to suit 100, 120, 220 or 240V and re-inserted. Despite having a mains transformer, the unit only weighs a modest 2.1kg</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><span>Secondly, the supplied mains cable has a US standard plug. This is not a problem though, as the connector is a standard IEC “kettle lead” and most labs have plenty of those hanging around! The <span><span id="addProduct-55tLwpP6-linked" style="white-space: nowrap;"><a class="jive-link-product-addtolist" href="" title="View product details"><span class="pf-widget-map pf-product-info-icon"></span></a><a class="jive-link-product pf-embedded-product-link" href="" title="View product details">DMM4020</a> </span></span> does have a set of stand-off feet moulded into the rear of the case, which allows it to be operated vertically rather than in the conventional horizontal manner. Unfortunately the supplied mains lead is a “straight through” rather than a 90 degree elbow, and so if you try to stand the meter upright, whether against the floor, desk or slotted into a rack, it sits on the cable rather than the feet, and so is unstable. Note to Tektronix : Supply a 90 degree "Elbow" power lead please!</span></div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal">One thing which is really good to see – a proper mains on/off switch mounted next to the power connector. So far as I can see from looking through the ventilation holes, this is a proper switch which isolates all internal components.</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
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</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: 14pt;"><strong style="mso-bidi-font-weight: normal;">Construction</strong></span></div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;"><br />
</strong></div>As you can see from the photo, the DM4020 comes in Tektronix corporate colour. That familiar grey-blue colour which is so often seen around labs. The main body is pressed alloy construction, with plastic front panel. The front and rear both have flexible plastic/rubber protective “boots” which can be removed for rack mounting. As usual with this sort of equipment, there is a tilting bail which can be positioned in a number of angles, used as a carrying handle, or removed entirely. The HRC fuses are of the high quality you would expect, and are accessible by removing a small metal panel underneath the unit. A small plastic box covers the fuses themselves, presumably for insulation and blast containment. They don’t seem as well protected as they are in hand-held meters.<br />
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</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: 14pt;"><strong style="mso-bidi-font-weight: normal;">Internally</strong></span></div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;"><br />
</strong></div><div class="MsoNormal"><span>I don’t intend to take the <span><span id="addProduct-fpt7h7K6-linked" style="white-space: nowrap;"><a class="jive-link-product-addtolist" href="" title="View product details"><span class="pf-widget-map pf-product-info-icon"></span></a><a class="jive-link-product pf-embedded-product-link" href="" title="View product details">DMM4020</a> </span></span> apart, not least because that would entail breaking the calibration seals, which I am loathe to do. Fortunately, however, you can get a pretty good view of the insides just by looking through the ventilation slots. This is very much a unit for a clean lab and not a dusty shop floor which would risk contaminating the sensitive electronics in no time.</span></div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal">Visible in the middle off the board is the heated precision voltage reference, clearly labelled LM399H with a National Semiconductor logo. A well known and well respected precision voltage source, used in several meters in this market segment. Interesting that they didn’t choose an LM199 or LM299 which seem to be 2% initial tolerance versus the LM399’s 5%, although it has to be said that after calibration there is little difference. I suspect that putting the unit into standby from the front panel will keep the heater running inside the voltage reference whilst powering down the display and processor. This would seem an ideal compromise.</div><div style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
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</div><div class="MsoNormal"><span style="font-size: 14pt;"><strong style="mso-bidi-font-weight: normal;"><span style="font-family: Arial,Helvetica,sans-serif;">In use.</span> </strong></span></div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;"><br />
</strong></div><div class="MsoNormal"><span>As you can see from the front panel, the Tektronix <span><span id="addProduct-8D52W7c2-linked" style="white-space: nowrap;"><a class="jive-link-product-addtolist" href="" title="View product details"><span class="pf-widget-map pf-product-info-icon"></span></a><a class="jive-link-product pf-embedded-product-link" href="" title="View product details">DMM4020</a> </span></span> is a 5 ½ digit unit, with separate connections for low (200mA) and high current (10A) ranges. It is also capable of full 4-wire resistance measurement, although only a pair of</span><a class="jive-link-external-small" href="http://uk.farnell.com/tektronix/196-3520-00/test-leads-standard-tl710/dp/1771907" rel="nofollow" target="_blank"> Tek TL710</a> conventional probes are supplied. Supplied probes are usually low budget affairs, but these are really nice sharp Cat III/Cat IV 10A probes with finger shields. However - no ground clip is provided! This is definitely an oversight in a meter of this stature.</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal">One feature I will certainly be looking at is the ability to take two measurements at the same time, or sequentially. Some meters can perform functions such as AC voltage + Frequency, but not many can perform current + voltage measurements together, or DC+AC, such as might be used to monitor power supply ripple.</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal">You will note that it does not measure inductance or capacitance. I guess at this end of the market you would be expected to purchase a separate LCR meter.</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
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</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: 14pt;"><strong style="mso-bidi-font-weight: normal;">Performance</strong></span></div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;"><br />
</strong></div><div class="MsoNormal">These are the easiest to quantify in hard numbers. All this data is copied from the official (copious) Tektronix information, boiled down into the main points. I will go into more depth in the main review:</div><div style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;">Measurement Speed</strong></div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;"><br />
</strong></div><div class="MsoNormal">The DMM2040 can measure at 2.5, 20 or 100 samples per second. Normally 2.5 is perfectly sufficient, and 20 cannot be distinguished by human eye. However, this is good for capturing short transition events, or for high speed logging via the computer link. In the faster two modes, however, precision is truncated by one digit.</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;">DC Voltage</strong></div><div class="MsoNormal">Maximum input: 1000V<br />
Input bias current: <30pA @ 25C<br />
Input impedance: >10G Ohms (200mV and 2V ranges) 10M Ohms (20/200/1000V ranges)<br />
Resolution on 200mV scale:<span style="text-decoration: underline;"> 1uV</span><br />
Accuracy: +0.01% of reading + 0.003% of range</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><strong style="mso-bidi-font-weight: normal;"> </strong> </div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;">AC Voltage</strong> (True RMS)</div><div class="MsoNormal">Maximum input: 1000V peak, 750V RMS.<br />
Accuracy (all ranges 45Hz – 20kHz): 0.15% of reading + 0.05% of range</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><strong style="mso-bidi-font-weight: normal;"> </strong> </div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;">DC Current</strong></div><div class="MsoNormal">Input protection: 11A/1000V and 440mA/1000V fuses</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal">Shunt resistance: 0.01 Ohms (2A and 10A ranges)<br />
1 Ohm (20mA and 200mA)</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal">Resolution: 200uA scale: <span style="text-decoration: underline;">1nA (yes, that’s 1 nanoAmp)</span><br />
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Accuracy: typ. 2mA scale 0.015% of reading + 0.005% of range</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><strong style="mso-bidi-font-weight: normal;"> </strong> </div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;">AC Current:</strong> </div><div class="MsoNormal">AC Filter Bandwidth: 20Hz – 100kHz<br />
Maximum Crest Factor 3:1 at full scale<br />
Resolution: 20mA scale: 0.1uA (100nA)</div>Accuracy: Typ. 200mA scale, 45Hz-2kHz: 0.25% of reading + 0.05% of range.<br />
<div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><strong style="mso-bidi-font-weight: normal;"> </strong> </div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;">Resistance</strong></div><div class="MsoNormal">Specification for 4-wire function or 2-wire with REL (relative measurement)<br />
Input protection: 1000V on all ranges<br />
Resolution: 200 Ohm scale : 0.001 Ohm (1 milli-Ohm)</div><br />
<div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;">Frequency:</strong></div><div class="MsoNormal">Range: 20Hz – 1MHz, for input >100mV<br />
Accuracy: 0.01%</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;">Continuity:</strong></div><div class="MsoNormal">Threshold: 20 Ohms<br />
Test current: 1mA</div><div class="MsoNormal"><br />
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</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: 14pt;"><strong style="mso-bidi-font-weight: normal;">Unseen performance</strong></span></div><div class="MsoNormal"><span style="font-size: 14pt;"><strong style="mso-bidi-font-weight: normal;"><br />
</strong></span></div><div class="MsoNormal"><span>So much for the book data. With less than a week’s use, it is safe to say that I haven’t even scratched the surface on what the <span><span id="addProduct-dIvzaGli-linked" style="white-space: nowrap;"><a class="jive-link-product-addtolist" href="" title="View product details"><span class="pf-widget-map pf-product-info-icon"></span></a><a class="jive-link-product pf-embedded-product-link" href="" title="View product details">DMM4020</a> </span></span> can do, but I have found some very nice functionality that most users just wouldn’t notice unless they were looking for. Specifically:</span></div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;">Diode test</strong>.</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><span>Most diode test functions only work at 1-1.5V, enough to test ordinary signal diodes, but not enough to test LEDs. The <span><span id="addProduct-K7s0Imjp-linked" style="white-space: nowrap;"><a class="jive-link-product-addtolist" href="" title="View product details"><span class="pf-widget-map pf-product-info-icon"></span></a><a class="jive-link-product pf-embedded-product-link" href="" title="View product details">DMM4020</a> </span></span> reads up to 1.9999V and drives up to 0.8mA, sufficient for the LED to light quite brightly. In theory this is only enough for red /yellow/green LEDs, but in practise the unit will illuminate blue and white LEDs also, which I was not expecting, although it will not give a voltage measurement for these.</span></div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;">Zero-burden Microammeter</strong>.</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal">Most engineers will be aware that the usual way of measuring current is to insert a small resistance into the circuit and measure the voltage drop across it. At low currents this can be quite a high resistance, leading to a “burden” voltage drop which is unacceptable and may even upset the circuit under test.</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal">The correct way to do this is with a transimpedance amplifier which provides almost no voltage drop, but can only realistically be performed at low current levels. It is quite a complicated thing to get right in a design and, as a result, is only usually seen in expensive dedicated microammeters. The Tektronix DM4020 is the only meter that I know of (this side of £1000 anyway) which uses this preferred method for measurement. If you often measure low currents, this feature alone may be worth the price of the meter.</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;">Relay Range Switching.</strong></div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;"><br />
</strong></div><div class="MsoNormal"><span>In order to switch in appropriate shunts and multipliers, the <span><span id="addProduct-MqOvgz23-linked" style="white-space: nowrap;"><a class="jive-link-product-addtolist" href="" title="View product details"><span class="pf-widget-map pf-product-info-icon"></span></a><a class="jive-link-product pf-embedded-product-link" href="" title="View product details">DMM4020</a> </span></span> uses proper electromechanical relays rather than silicon switches. This slows down auto ranging, but not unacceptably so. Manual override is always available and is probably preferred in most cases. Relay switching is by far the best method in equipment where you are looking for measurement performance and have the luxury of a large PCB real estate and a mains power supply.</span></div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;">“Other Stuff”</strong></div><div class="MsoNormal"><strong style="mso-bidi-font-weight: normal;"><br />
</strong></div><div class="MsoNormal">The supplied LabView software is a little clunky to install (and partially deactivates after a preview period) but does work pretty well. I am no LabView expert, but I can see how relatively easy it is to automate tasks if you are working in a production environment. This is definitely one thing I will be looking more closely at. Simply logging data in ASCII format to a text file is very handy indeed.</div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><span>In order to connect the <span><span id="addProduct-sjTcuh36-linked" style="white-space: nowrap;"><a class="jive-link-product-addtolist" href="" title="View product details"><span class="pf-widget-map pf-product-info-icon"></span></a><a class="jive-link-product pf-embedded-product-link" href="" title="View product details">DMM4020</a> </span></span> to the outside world, it is fitted with a standard RS232 port at the rear. Tektronix thoughtfully provide an RS232-to-USB adaptor, with a good 2M of cable. This seems to be based on an FTDI chip, which in my experience has proven most reliable in this sort of role. Windows 7 picked it up straight away and downloaded drivers via Windows Update.</span></div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
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</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: 14pt;"><strong style="mso-bidi-font-weight: normal;">Conclusion</strong></span></div><div class="MsoNormal"><span style="font-size: 14pt;"></span></div><div class="MsoNormal"><span style="font-size: 14pt;"><strong style="mso-bidi-font-weight: normal;"></strong></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><span>So there we are. Four days use and a “quick” look that is already several pages long. That gives you an idea about what sort of machine the Tektronix <span><span id="addProduct-69znG70z-linked" style="white-space: nowrap;"><a class="jive-link-product-addtolist" href="" title="View product details"><span class="pf-widget-map pf-product-info-icon"></span></a><a class="jive-link-product pf-embedded-product-link" href="" title="View product details">DMM4020</a> </span></span> is, I hope that I have at least been able to give a taste of what this machine can do. I hope to have a much more in-depth review up in a few weeks, after it has had some use in a real world situation. One of the things I have lined up is the development of my LCR meter project. Having a meter this accurate will help immensely.</span></div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
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</div><div class="MsoNormal"><strong style="font-size: 14pt;">A Request</strong></div><div class="MsoNormal" style="height: 8pt; min-height: 8pt; padding: 0px;"><br />
</div><div class="MsoNormal"><span>I want to shoot some video of the <span><span id="addProduct-8y3YV2ht-linked" style="white-space: nowrap;"><a class="jive-link-product-addtolist" href="" title="View product details"><span class="pf-widget-map pf-product-info-icon"></span></a><a class="jive-link-product pf-embedded-product-link" href="" title="View product details">DMM4020</a> </span></span> in action if I can. At the moment I only have a webcam and a cheap compact camera that will shoot video, so I am looking to buy myself a reasonable 720 or 1080 digital video camera. Does anyone have any recommendations? I don’t want to spend more than maybe £150 or so, it doesn’t need to be a fantastic spec. Thanks!</span></div><div class="MsoNormal"><br />
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</div><div class="MsoNormal"><span>Additional: Farnell / Element-14 tell me that UK purchasers will have their meter pre-configured for UK 240V power. </span></div><div class="MsoNormal"><br />
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</div>Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com2tag:blogger.com,1999:blog-3933619678696660447.post-46739168861295717792011-09-27T17:18:00.000+01:002011-09-27T17:18:40.706+01:00HP-15C now in Stock at HP! No it isn't! Yes it is ! No it isn't!Well, the HP-15C finally made it to market, and promptly sold out within a few hours. So quickly, in fact, that I didn't even get a chance to post it here before they had all gone. From the look of Ebay, many seem to be bought by speculators.<br />
<br />
Anyway, they are back on sale at <a href="http://www.shopping.hp.com/webapp/shopping/can.do?landing=calculator&category=Scientific&catLevel=1&storeName=storefronts">HP's online store</a>. Oh wait... No they aren't. This time the stock lasted about half a day. All I can say is - keep an eye out for when they restock! My guess is that if they keep selling this quickly, then the Limited Edition won't be quite so limited.<br />
<br />
Amazon.com look to have them in stock. 4 left at the time of writing, listed at a mere $119:99. $20 more than the official HP shop, albeit Amazon have free shipping. Can we say "gouging"? I thought so. Still, it is cheaper than Ebay.<br />
<br />
I don't think I will be buying one, I find the missing binary / hex modes too useful. Any chance of the HP-16C? Potential purchasers might like to be aware that the build quality is typical Kinpo Electronics rather than classic Hewlett Packard.<br />
<br />
<br />
<div class="separator" style="clear: both; text-align: center;"><img border="0" src="http://hpshopping.speedera.net/s7d2.scene7.com/is/image/HPShopping/big_fmt/nw250aa_main.jpg" /><a href="http://www.shopping.hp.com/webapp/shopping/can.do?landing=calculator&category=Scientific&catLevel=1&storeName=storefronts"></a></div>Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com2tag:blogger.com,1999:blog-3933619678696660447.post-50497371494807140692011-09-14T01:41:00.001+01:002011-09-14T01:46:53.045+01:00A PCB CAD Refresher CourseAt one time it felt like I was destined to be a PCB designer, churning out design after design for someone else's work. Now this is a very worthwhile and skilled job, but it wasn't for me, and so it is only occasionally that I get to design PCBs now. Unfortunately that means that I tend to forget work-flows, and fiddly little quirks and details. Come to think of it, I tend to forget some pretty big details too! When you have let muscle memory get on with things, it can be daunting when you come back to your CAD software. <br />
<br />
I have a fair few notes which I have written up over the years, and I was even considering recording a video. This started me wondering what YouTube might have to offer. Altium have done a load of videos (hosted on their own site), but I have to say they aren't very helpful. At best they are rather "corporate". Anyway, to cut a long story short, I found these YouTube videos. They are clearly recorded by someone who knows what he is doing, and aimed at the more introductory end, but are very much worth watching if you need a quick refresher.<br />
<br />
<br />
All these videos relate to Altium Designer, and are best viewed full screen. Videos recorded by http://www.youtube.com/user/elektroniskorg<br />
<br />
1. <a href="http://www.youtube.com/watch?v=Y7PY1nBtImk">Schematic capture and PCB layout (Part 1)</a><br />
<br />
<div class="separator" style="clear: both; text-align: center;"><iframe allowfullscreen='allowfullscreen' webkitallowfullscreen='webkitallowfullscreen' mozallowfullscreen='mozallowfullscreen' width='320' height='266' src='https://www.youtube.com/embed/Y7PY1nBtImk?feature=player_embedded' frameborder='0'></iframe></div><br />
2.<a href="http://www.youtube.com/watch?v=9u0Fzpb0yZU"><span class="long-title" dir="ltr" id="eow-title" style="vertical-align: top;" title="Altium Designer Tutorial: Schematic capture and PCB layout (2of2) (improved)">Schematic capture and PCB layout (Part 2) </span></a><br />
<br />
<div class="separator" style="clear: both; text-align: center;"><iframe allowfullscreen='allowfullscreen' webkitallowfullscreen='webkitallowfullscreen' mozallowfullscreen='mozallowfullscreen' width='320' height='266' src='https://www.youtube.com/embed/9u0Fzpb0yZU?feature=player_embedded' frameborder='0'></iframe></div><br />
3. <a href="http://www.youtube.com/watch?v=pW_kpk5lQlM">Creating a Component Library</a><br />
<br />
<div class="separator" style="clear: both; text-align: center;"><object class="BLOGGER-youtube-video" classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,40,0" data-thumbnail-src="http://3.gvt0.com/vi/pW_kpk5lQlM/0.jpg" height="266" width="320"><param name="movie" value="http://www.youtube.com/v/pW_kpk5lQlM&fs=1&source=uds" /><param name="bgcolor" value="#FFFFFF" /><embed width="320" height="266" src="http://www.youtube.com/v/pW_kpk5lQlM&fs=1&source=uds" type="application/x-shockwave-flash"></embed></object></div> <br />
4. <a href="http://www.youtube.com/watch?v=hew6bPADJZ0">Navigating Designs</a><br />
<br />
<div class="separator" style="clear: both; text-align: center;"><iframe allowfullscreen='allowfullscreen' webkitallowfullscreen='webkitallowfullscreen' mozallowfullscreen='mozallowfullscreen' width='320' height='266' src='https://www.youtube.com/embed/hew6bPADJZ0?feature=player_embedded' frameborder='0'></iframe></div><br />
5. <a href="http://www.youtube.com/watch?v=OaefGeQrRkA">Working with Vias and Multiple Layers</a><br />
<br />
<div class="separator" style="clear: both; text-align: center;"><iframe allowfullscreen='allowfullscreen' webkitallowfullscreen='webkitallowfullscreen' mozallowfullscreen='mozallowfullscreen' width='320' height='266' src='https://www.youtube.com/embed/OaefGeQrRkA?feature=player_embedded' frameborder='0'></iframe></div><br />
<br />
6. <a href="http://www.youtube.com/watch?v=pg6l02Rinos">Copper Planes and Pours</a><br />
<br />
<div class="separator" style="clear: both; text-align: center;"><iframe allowfullscreen='allowfullscreen' webkitallowfullscreen='webkitallowfullscreen' mozallowfullscreen='mozallowfullscreen' width='320' height='266' src='https://www.youtube.com/embed/pg6l02Rinos?feature=player_embedded' frameborder='0'></iframe></div>Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-75678700891692829692011-07-24T05:37:00.000+01:002011-07-24T05:37:41.370+01:00Advanced Calculations<b><span style="font-family: Arial,Helvetica,sans-serif; font-size: large;">(Or how 1989 - 2011 = 15+30+34+41 ) </span></b><br />
<br />
Thanks to <a href="http://blog.makezine.com/">Make Magazine Blog</a> for mentioning my article on calculators (see <a href="http://electronicsdesigner.blogspot.com/2011/05/difficult-calculations.html"><i>Difficult Calculations</i></a> ). It seems that I am not alone in my calculator geekery. Page views shot up by a factor of 100x in a couple of hours!<br />
<br />
Inevitably though, no sooner had I written the article than things started to move on. It looks like Hewlett Packard aren't totally devoid of sense after all. Thanks to Dave Jones of the EEVBlog for pointing me in the direction of this:<br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEii0iW1ZD9h9Nd3SdZiZUGkoFEAmDHIpRLCdh31Y7QvLaqZVN-uz4f2yctivPBGh3fNitaexN8oWCAcmuX7qvyRjjzn1urhOgrPuB2ydxTIn5FzGmn9rYV8c-_cXZxeOht-YZhEaCArWUBi/s1600/HP-Site.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEii0iW1ZD9h9Nd3SdZiZUGkoFEAmDHIpRLCdh31Y7QvLaqZVN-uz4f2yctivPBGh3fNitaexN8oWCAcmuX7qvyRjjzn1urhOgrPuB2ydxTIn5FzGmn9rYV8c-_cXZxeOht-YZhEaCArWUBi/s400/HP-Site.jpg" width="400" /></a></div><br />
Yes, this is from the real Hewlett Packard web site. This is a screenshot of the Google cache (see here) of HP's Singapore web site. (Screenshotted just in case the cache gets overwritten) Similar pages were on other nations HP sites too, including the Indian version. I checked, and it all looks legitimate and not a spoof. At the time of writing, HP still hosts a photograph of the calculator in question, an HP-15C:<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://product-images.www8-hp.com/digmedialib/prodimg/lowres/c02892366.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="http://product-images.www8-hp.com/digmedialib/prodimg/lowres/c02892366.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">HP-15C Limited Edition</td></tr>
</tbody></table><br />
Investigations by the forum members at the <a href="http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/forum.cgi?read=187991#187991">HP Museum</a> site have revealed that the "HP-15C Limited Edition" will shortly be on sale in Japan. No information is available as to whether they will be shipping them in other countries.If they do appear in the UK, then one is going straight on my shopping list. <br />
<br />
It looks like a pretty close copy of the original, but the brushed aluminium bezel around the display has been replaced with what looks like white plastic, and the printing somehow looks less crisp. My guess is that Kinpo have been brought in once again by HP, and rather than simply producing a copy of the original, they have re-engineered it to maximise cost savings. Something which has rather back-fired on them in the past. As it stands, the (still in production) HP-12C internals have been converted to an ARM processor based system for some time, so a new version of the 15C and 16C should be straight forward. <br />
<br />
Back in the 80s, the HP-15C cost $135. It looks like the new version will sell for an RRP of $129. That is fine in the US, the land of discounts and coupons, but I suspect it will come out at £129 here in the UK after taxes. Given that the HP-15C is based the same hardware used by the HP-12C ($70) then it starts to look a bit expensive. It is a shame that they didn't go the extra mile and produce the HP-16C too, which adds binary and hexadecimal functionality.<br />
<br />
<b><span style="font-family: Arial,Helvetica,sans-serif; font-size: large;">The WP-34S</span></b><br />
<br />
It looks like the HP-12C re-purposing project (that's the polite term for hacking now) has stalled (<a href="http://www.wiki4hp.com/doku.php?id=12c:repurposing_project">see here</a>) but the project to investigate the potential of the HP-20B and HP-30B business calculators seems to have moved onwards very quickly indeed (<a href="http://sourceforge.net/projects/wp34s/">see here</a>), enabling vastly more functionality, based around the HP-42S core software, but very much expanded upon. In fact, it does so much more, that the developers have had to print a whole new set of key legends:<br />
<br />
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="http://h10003.www1.hp.com/digmedialib/prodimg/lowres/c01839761.jpg" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="320" src="http://h10003.www1.hp.com/digmedialib/prodimg/lowres/c01839761.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Original HP-30b</td></tr>
</tbody></table><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.blogger.com/goog_1031608116" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="320" src="http://www.thecalculatorstore.com/WebRoot/StoreES3/Shops/eb9376/MediaGallery/DSC_7897_L.jpg" width="212" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><a href="http://www.thecalculatorstore.com/WebRoot/StoreES3/Shops/eb9376/MediaGallery/DSC_7897_L.jpg">Modified with WP-34SFirmware and key legends</a></td></tr>
</tbody></table><br />
Yes, these are the same calculator. I do wonder just how robust the stickers are, but reports seem generally favourable. A complete reprogrammed calculator + overlays is on sale at £76:98 / €84:68. The firmware manual / user guide is available <a href="http://sourceforge.net/projects/wp34s/files/doc/">here</a>.<br />
<br />
Do you know what I love about it though? It has markings on the keys - and this is the important bit - I don't know what they all mean. Seriously, I have a row of letters after my name, I have been doing engineering maths for decades, but yet there is stuff in there that is a mystery to me. Sure, it is statistical stuff that I will never need, but that doesn't matter, it means someone is finally adding new functionality to calculators. It makes me feel a bit like when I was a kid with my nose pressed against the window of the glass cabinet with all those mystical electronic boxes inside.<br />
<br />
<span style="font-family: Arial,Helvetica,sans-serif; font-size: large;"><b>So that is 15, 30, and 34 dealt with (see the blog title), how about 41?</b></span><br />
<br />
Well, processor designer Monte J. Dalrymple has reverse engineered the HP-41C, and then created an improved version of it on an FPGA. I mean - seriously - it doesn't get much more hardcore than that does it?<br />
<br />
Lots more information <a href="http://systemyde.com/hp41/">here on Monte's site</a>. <br />
<br />
The thing is, all the essential hardware is on an FPGA. It is a relatively (and I use the term recklessly) easy job to hook up your own LCD and keypad, and you have your own HP-41C clone. All it needs is a millionaire willing to stump up enough money to make moulds for the enclosure. Some things have simply <i>got </i>to be done.<br />
<br />
Suddenly, the world of calculators just got more interesting.Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-11494113231885014162011-06-16T18:35:00.000+01:002011-06-16T18:35:55.497+01:00Hewlett-Packard Calculator TimelineAs part of my previous blog post on calculators, I had started to draw up a graphical representation of calculator evolution. My intention was to include TI, Sharp, Casio etc (hence the timeline starting at 1960) but considering this subset of HP calculators took several hours, I decided a full comparison probably wasn't worth the effort. Given the popularity of the previous item, I thought some people may be interested. It doesn't include all HP calculators by any means, finishing with the HP-48S.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/HP-Calculator-Timeline.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="282" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgidfdi4Q-WNt5ETtkZCieN14FwgJtMerMnS4fMSrVK-gRtjhQAU6MskWIa3jIAH_wRNxmHV1zS-VWYeG-NViQE0Gr9mdZHKbgx4sEhXAF3eHgJ9pJXaQSfI3TWb52tmh7WpRgOnuFivroE/s400/HP-Calculator-Timeline.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Hewlett-Packard Calculator Timeline</td></tr>
</tbody></table>Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-44560122766226482672011-05-31T01:27:00.000+01:002011-06-01T03:57:47.974+01:00Difficult Calculations<div class="MsoNormal">I suspect I was part of the first generation to have been brought up with “pocket” calculators (“pocket” to distinguish them from desktop mechanical calculators the size of a bread bin). I vaguely remember seeing them in my dad’s electronics magazines, sometime around 1979. One Christmas around then, my dad was bought one which has a fluorescent blue/green display which really looked super high-tech, and is still a really pleasing design. Although it was only a classic four-function machine (add, subtract, multiply, divide) I really coveted it, but it was couple of years before I got my own calc. </div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://i.ebayimg.com/00/$%28KGrHqR,%21kwE1LC7oFIqBN,vyzJWNg%7E%7E_12.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="http://i.ebayimg.com/00/$%28KGrHqR,%21kwE1LC7oFIqBN,vyzJWNg%7E%7E_12.JPG" width="224" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Late 1970s Vintage LED Calculator<br />
(Similar to mine)</td></tr>
</tbody></table>I remember going to one of the electronics exhibitions that the magazines helped organise – possibly “<i style="mso-bidi-font-style: normal;">Breadboard ’79”</i> – where a stall was selling classic red-LED calculators for £2:99. Not only did it have the standard four functions, but a memory too. Wow, that was practically a computer! Other than the 7-segment, 8-digit display, the thing I remember most about it was the clicky keys. Noisy, but really good tactile feedback and, even on a super cheap calculator, it gave a feeling of confidence and precision. The 9V PP3 battery didn’t last more than maybe 10 hours, but it was long enough. </div><div class="MsoNormal"><br />
</div><div class="MsoNormal"></div><div class="MsoNormal">Of course the first thing I did when I got it home was to release the plastic moulded latches (no screws holding the case together) and take it apart. I was disappointed to find it had just one chip, and some convex metallic pads mounted directly on the PCB to act as switches. I felt ripped off that there weren’t half a dozen chips and proper switches, but it was all highly engineered compared with today’s products.</div><div class="MsoNormal"><br />
</div><div class="MsoNormal">It was maybe a couple of years later, when I had moved up to the “big” school, that I discovered my form teacher had a <i style="mso-bidi-font-style: normal;">programmable</i> calculator. Woah! I had read about programmable calculators in magazines like <i style="mso-bidi-font-style: normal;">PCW</i> and Computing, and I had seen them locked away in glass cases in Boots in Leeds (for some reason Boots the chemist always had better calculators than the electronics stores of the time) but I had never seen one close up before. From what I remember, I think it must have been a Hewlett Packard HP-67, but I never got to see it again. The teacher had left it on charge at the back of the classroom over lunchtime, and some idiot had switched it off while the teacher was out of the room . She never (probably quite rightly) trusted us again.</div><div class="MsoNormal"><br />
</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Hp_67_powered.jpg/390px-Hp_67_powered.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Hp_67_powered.jpg/390px-Hp_67_powered.jpg" width="208" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Retro Calculator Sexiness <br />
The HP67 programmable</td></tr>
</tbody></table><div class="MsoNormal"><br />
</div><div class="MsoNormal"> Time moved on, and a year or so later I had saved up enough money to buy myself a Casio fx-3600p. Liquid crystal displays had pushed out the power-hungry LED machines, and my trusty Casio looks just like an average calculator you would buy today. Indeed it is only recently that Casio only stopped production of this model. Incredibly, it is still running on the same battery it came with. If I hadn’t experienced it personally, I would have said a 30-year battery life was impossible, but there you are. On the back it quotes “DC 3V 0.00043W”, something modern manufacturers still have trouble approaching today. The fx-3600p is programmable, but with only a 38 step memory and no alpha characters it’s programmability is rather limited to say the least.</div><div class="MsoNormal"><br />
</div><div class="MsoNormal">As with many kids of the time I had a Casio CA-90 calculator watch (with a built in game that was surprisingly popular with the non-geeks at break times), and then a CFX-20 scientific calculator watch. Geeky? Hell yes. It even has a dot-matrix display which tells you what scientific or conversion function you have selected. Bloody good watch though, and I still have the slightly posher version, the chrome CFX-200. For some reason, I never particularly liked the styling of the CFX-40/CFX-400 which added potentially useful binary, octal and hexadecimal functions, but a cheap looking touch keypad.</div><div class="MsoNormal"><br />
</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="http://farm4.static.flickr.com/3116/2879502605_10be283693_z.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="195" src="http://farm4.static.flickr.com/3116/2879502605_10be283693_z.jpg" width="200" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">1983 Casio CFX-200 Scientific Calculator Watch <br />
(on my hairy wrist.)</td></tr>
</tbody></table><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://upload.wikimedia.org/wikipedia/commons/b/b5/Cfx400c.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="200" src="http://upload.wikimedia.org/wikipedia/commons/b/b5/Cfx400c.JPG" width="169" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Casio's later CFX-400 model with touch keypad. <br />
Note the hex/octal/binary and logic functions.</td></tr>
</tbody></table><div class="MsoNormal"><br />
</div><div class="MsoNormal"> Sadly, that was the end of the line as far as calculator watches went. Casio decided to make “memory bank” and TV remote control watches instead. You can still get calculator watches of course, but they don’t even have the abilities I had in my 1983 scientific machine.<br />
<br />
<a href="http://www.calcwatch.com/HP-02small.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="150" src="http://www.calcwatch.com/HP-02small.jpg" width="200" /></a>It would be remiss of me if I didn't mention at this point, Dave Jones' <a href="http://www.calcwatch.com/index.html">programmable scientific calculator watch design</a>. I think Dave would be the first to admit it isn't exactly stylish fashion jewellery, but it is a phenomenal bit of work. It even plays a game of chess for goodness sake! Just imagine what Casio or Seiko could do with a bit of willpower and a million dollars or so. <br />
<br />
</div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><br />
<br />
Eventually I did my A-levels and decided that, for Uni, I deserved a better calculator and bought a fearsomely expensive and highly desirable Casio graphing calculator, the fx-7000g. So desirable that it lasted nearly 6 months before being nicked, and I went back to my fx-3600p. In all honesty, the fx-7000g wasn’t a great machine. Sure it did graphs, but then I know what graphs of sine waves, X^2 and so on look like anyway. I did get it to plot Mandelbrot and Julia set fractals, but that took forever, and a 1-bit greyscale can never do them justice. The huge screen just made it look clunky. In hindsight, this is where calculator design started to drive up a blind alley.</div><div class="MsoNormal"><br />
</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://cdn.wn.com/pd/c6/ea/e5fa62c6648a6bde0402584c702c_grande.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="240" src="http://cdn.wn.com/pd/c6/ea/e5fa62c6648a6bde0402584c702c_grande.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Casio fx-7000G Graphing Calculator</td></tr>
</tbody></table><div class="MsoNormal"> </div><div class="MsoNormal">The temptation didn’t last long though, and a friend of mine had a Hewlett-Packard HP-28C. Properly programmable with a real programming language, small bitmapped display, alpha-numeric keys, hex/octal/binary, arrays, complex numbers and, most importantly, it had proper clicky keys and operated using the mystical Reverse Polish Notation – RPN. The absolute pinnacle of the calculator world. I spent a huge chunk of my first term’s grant on the 28C’s faster and more capacious offspring, the 28<i style="mso-bidi-font-style: normal;">S</i>. Thanks to the RPN, people only ever borrowed it once, and it never got stolen. It was worth every penny, HP had a track record of making well engineered calculators for people who use them every day. Calculators for engineers and scientists, not calculators for 14 year olds.</div><div class="MsoNormal"><br />
</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/IMG_2537.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="213" src="http://i222.photobucket.com/albums/dd237/Zadpics/IMG_2537.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">My Hewlett Packard HP-28S and Casio fx-3600P Programmable Calculators<br />
(with obligatory schoolboy humour)</td></tr>
</tbody></table><div class="MsoNormal"><br />
</div><div class="MsoNormal"><br />
</div><div class="MsoNormal">I still have both the fx-3600p and HP-28S, but more importantly though, I still regularly use them. The Casio needs it’s contacts cleaned once a year and the Hewlett Packard is also a pain because it uses three relatively expensive batteries which only last about 2 years.</div><div class="MsoNormal"><br />
</div><div class="MsoNormal">After HP brought out the HP-28S, the calculator world seemed to go into stasis. Most new models were aimed at the finance market and, as schools and colleges had banned programmable models, I guess there was little incentive to make progress.</div><div class="MsoNormal"><br />
</div><div class="separator" style="clear: both; text-align: left;">In recent years I have looked at the HP-48/49/50 and derivatives, with better displays and progressively larger memory and faster processors, but nothing that really felt like progress. Texas Instruments (TI) have come out with some powerful beasties with all sorts of functions but, again, nothing that really floated my boat. Except…</div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><a href="http://tezxas.ticalc.org/pictures/mminer92.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" src="http://tezxas.ticalc.org/pictures/mminer92.jpg" /></a>…<a href="http://tezxas.ticalc.org/platform.htm">Someone managed to get Manic Miner running on the TI-89 and 92+</a>. I was seriously tempted at that point. But it was still very limited grey-scale, and looked more like a toy than a serious tool for science and engineering. My fx-3600p and HP-28S may be old, but they look like they were designed to do a job and to work for a living, not like My-First-Mobile-Phone for 4 year olds.</div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-size: large;">Yes, But What's The Point Of All This? </span></b></div><div class="MsoNormal"><br />
</div><div class="MsoNormal">So, why am I saying all this? I mean, a chunk of life story is all very nice if you are my mother, and a whinge is good for letting off steam (come on, this <i style="mso-bidi-font-style: normal;">is</i> a blog) but what is my point? Well, my calculators aren’t getting any younger or more reliable, so I am now reluctantly in the process of looking around for a new one.</div><div class="MsoNormal"><br />
</div><div class="MsoNormal">Below, you can see a couple of pages from the 1984 edition of the seminal consumer work The 1984 Argos Catalogue (aka the laminated book of dreams). See the selection available? There are seven programmables and many more scientifics. Now – not a single programmable one. These people sell full SLR cameras, iPods, iPhones, iPads, laptops and a million and one mobile phones, but just 8 scientific calculators.</div><div class="MsoNormal"><br />
</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.blogger.com/goog_761860415" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="199" src="http://i222.photobucket.com/albums/dd237/Zadpics/Argos1984.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/Argos1984.jpg">Argos Catalogue 1984 - Calculators</a></td></tr>
</tbody></table><div class="MsoNormal"><br />
</div><div class="MsoNormal"><br />
</div><div class="MsoNormal">So I looked a little further afield, and went to the manufacturers’ web sites to have a look at their key models.</div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><a href="http://www.blogger.com/goog_761860436"><span style="font-size: large;"><b>Hewlett-Packard</b></span> </a></div><div class="MsoNormal"><a href="http://www8.hp.com/uk/en/products/calculators/index.html">HP-35S, HP-39GS, HP-40GS, HP-48GII.</a></div><div class="MsoNormal"><br />
</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.blogger.com/goog_761860428" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="213" src="http://www.ecalc.com/pics/calcs/HP-50G/HP-50G_2.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><a href="http://h41111.www4.hp.com/calculators/uk/en/graphing/50g/index.html">HP-50G Calculator</a></td></tr>
</tbody></table><div class="MsoNormal"><br />
</div><div class="MsoNormal"></div><div class="MsoNormal">With the top of the range model, the<a href="http://h41111.www4.hp.com/calculators/uk/en/graphing/50g/index.html"> HP-50G </a>(pictured above). All these calculators are based on the ARM-9 powered HP-49 architecture and are manufactured on behalf of HP by Chinese company <a href="http://www.newkinpogroup.com/eng/">Kinpo</a>. As you might expect, the quality took a nose-dive when HP stopped performing their own R&D and manufacturing, some time around 2003, with various complaints about a lack of key feedback, software bugs, and general build quality. Even Kinpo's web site seems to be bugged and missing pages. </div><div class="MsoNormal"><br />
</div><div class="MsoNormal">Although they have improved the key feel in recent model revisions, the HP-50G still spurns the traditional (and excellent) shaped buttons which HP used in their earlier models. The up/down/left/right and function buttons also look rather dated in the age of touch screens. Note also how big it is in an adult male's hand. The UK price is a fairly reasonable £90 (new on Ebay, May 2011 price) or <a href="http://www.amazon.co.uk/Hewlett-Packard-HP50G-Graphing-Calculator/dp/B000GTPRPS">£90:34 excluding P&P on Amazon</a>, but it looks too much like a toy to be taken seriously. Sure it has an SD card socket (not SDHC) and infra-red comms, but in these days of Bluetooth and WiFi those features only succeed in making it look even more outdated. A sad end to a noble brand. </div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><a href="http://education.ti.com/educationportal/sites/US/sectionHome/calculators.html"><span style="font-size: large;"><b>Texas Instruments</b></span></a></div><div class="MsoNormal"><a href="http://education.ti.com/educationportal/sites/US/sectionHome/calculators.html"></a></div><div class="MsoNormal">TI-83+, TI-84+ (Z80 based)<br />
TI-89 Titanium, TI-92 and Voyage 200 (68000 based)<br />
TI-Nspire series (ARM based): Clickpad, Clickpad+CAS, Touchpad, Touchpad+CAS, CX, CX+CAS</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><br />
</td><td style="text-align: center;"><br />
</td></tr>
<tr><td class="tr-caption" style="text-align: center;"></td></tr>
</tbody></table><div class="MsoNormal">The TI 73/83/84/89 Look very similar to the HP graphing calculators, so it is a fair bet that they are after the same market segment. The TI-89's design is notable in that they seem to have angled the keys closest to the edge, making them look a bit like a mobile phone design from a few years ago.</div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://education.ti.com/images/rightcolumn/products/graphing/TI89Titanium_L.jpg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" src="http://education.ti.com/images/rightcolumn/products/graphing/TI89Titanium_L.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Texas Instruments<br />
TI-89 Titanium</td></tr>
</tbody></table>The TI-92 and Voyage(tm) 200 have an added QWERTY keypad (I can't really call it a keyboard). The effect is that it looks like it has been designed by a committee of 12 year olds who wanted EVERYTHING. NOW. We will hear more from these 12 year olds shortly... Quite honestly, if you can cope with something the size of the Voyage 200, then you should probably be using a netbook.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://education.ti.com/images/rightcolumn/products/graphing/Voyage200_L.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://education.ti.com/images/rightcolumn/products/graphing/Voyage200_L.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Texas Instruments TI Voyage 200<br />
"Design - We've heard of it"</td></tr>
</tbody></table></div><div class="MsoNormal"></div><div class="MsoNormal"><br />
And now... (big fanfare)... The TI-Nspire Series. When I heard about the new TI Nspire series of calculators, I got really excited, and that isn't something that happens a lot with me (as you can imagine). ARM processor, full colour high resolution backlit LCD, real time 3D graphing, integrated rechargeable battery, USB, all in a slim case. Brilliant! I thought "This is what the market needs, something to move things into the 21st century, the calculator for the iPhone generation". Then I saw it. Oh mother...<br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://www.underwooddistributing.com/shop/components/com_virtuemart/shop_image/product/Add_l_Nspire_CX__4d9233399de0e.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="http://www.underwooddistributing.com/shop/components/com_virtuemart/shop_image/product/Add_l_Nspire_CX__4d9233399de0e.jpg" width="239" /></a></div><br />
The committee of 12 year olds are now 14 year olds, and they still want EVERYTHING. Except design, style, taste, and usability. The TI Nspire CX is 200x100x27mm. That is over an inch thick and 32 square inches of desk space. I calculate that it is double the volume of my already chunky HP-28S. And besides – look at the thing! Just in case you are under the mistaken impression that it is still pocket calculator sized, here is another view courtesy of TI:<br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://thetechjournal.com/wp-content/uploads/2011/03/110228-nspire-01.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="250" src="http://thetechjournal.com/wp-content/uploads/2011/03/110228-nspire-01.jpg" width="320" /></a></div><br />
Hang on - didn't TI say this thing was <i>slim</i>? My iPod touch is 8mm thick, this Nspire CX is 27mm. What are you talking about TI? It is very telling that TI is aiming these at the "educational" market. In other words, school children.Great, but what about us people who have left school and are now working for a living? Add to this the reluctance, actually no not reluctance - fear - TI seem to have of independent developers (call them hackers, makers, developers or for that matter simply enthusiastic owners) then I think we can remove all TI products from our virtual list of potential calculators.<br />
<br />
Anyone considering playing around with TI calculators should read this:<span style="font-size: small;"> <a href="http://www.techdirt.com/articles/20110521/17265314378/texas-instruments-learns-nothing-goes-after-hobbyists-again.shtml">Texas Instruments Learns Nothing, Goes After Hobbyists Again</a></span><br />
<br />
and this:<a href="http://blog.makezine.com/archive/2011/05/ti-vs-calculator-hobbyists-again.html"><span style="font-size: small;"> TI vs. Calculator Hobbyists – AGAIN</span></a><br />
<br />
TI seem to be in the increasingly large collection of companies which are under the impression that they can control the Internet. This tells me that lawyers are running the company, not engineers.<br />
<br />
<br />
</div><div class="MsoNormal"><a href="http://www.casio.co.uk/products/Calculators/"><span style="font-size: large;"><b>Casio </b></span></a></div><div class="MsoNormal"><br />
<div class="MsoNormal">FX-CG10 (FX-CG20) (new), <br />
FX-9860GII (new), FX-9860GII SD (new),<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.casio.co.uk/handlers/RenderMediaItemData.ashx?id=61577" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="200" src="http://www.casio.co.uk/handlers/RenderMediaItemData.ashx?id=61577" width="158" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Casio fx-9860GII SD</td></tr>
</tbody></table>FX-9750GII (new), FX-9750G+,<br />
FX-7400G+<br />
CFX-9850GC+<br />
FX-9860G, FX-9860G SD</div></div><div class="MsoNormal"><br />
</div><div class="MsoNormal">That's a lot of calculators, and a lot of "number and letter soup". Too much, to be honest. Especially if you add the SD card options. I'm generally not keen on the curvy pseudo-phone look of the case, but at least the FX-9860GII adds -<i>gasp</i>- a backlight! Still, it is only a clunky monochrome screen with the usual set of applications we see elsewhere. I'm pushed to distinguish it from the HP-50G and TI calculators. It probably looks a bit more professional than the TI machines, but only marginally.<br />
<br />
</div><div class="MsoNormal">Fortunately, Casio appear to be changing direction. Presumably being forced by the appearance of TI's colour screen devices. The PRIZM FX-CG10. Urgh, not only a mis-spelled word, but in capitals too. For added confusion, it will be known as the FX-CG20 in the UK. I guess their marketing guys had to invent more work for themselves.<br />
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.phonenews.com/wp-content/uploads/2011/01/Prizm-fx-cg10.jpg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="320" src="http://www.phonenews.com/wp-content/uploads/2011/01/Prizm-fx-cg10.jpg" width="300" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Casio PRIZM FX-CG10/CG20</td></tr>
</tbody></table>Anyway, the FX-CG10/20 at least looks like it belongs in this century. They still seem to feel compelled to make the keys look like something from a mobile phone, and the colour screen is obviously not a touch screen, but it is a good start. No processor type is stated (my guess would be one of the ARM family) and the screen is lower resolution than TI's Nspire uses, but it looks a whole lot more professional. Almost HP-like in fact. <i>Almost</i>.<br />
<br />
Will I be buying one though? Hell no. The UK price isn't too bad at £105, but it still doesn't do what I want it to do.<br />
<br />
A quarter of a century on from the launch of my HP28S, I think we deserve more. There is no shortage of mathematical horsepower from ARM chips, nor is there a problem with memory prices or displays. Touch screens should be standard, removing the need for function and cursor keys (in this instance, a resistive screen would be better than a capacitive one, allowing the user to enter symbols directly with a stylus) but numbers and core functions should be retained as proper hardware keys with shaped buttons. <br />
<br />
Software should be much more along the lines of the commercial heavyweights like Matlab or Mathematica. Wolfram Alpha is an obvious example of what the software should aim to be. I am not suggesting it be an iPod/Pad/Phone though, a calculator still needs to retain the immediate usability of conventional designs, whereby you can just flick a switch, and it is on and ready for use. Of course the real way of making it a killer product would be to open the OS and publish the hooks into the software, and to invite users to add to the available software. Pretty much the opposite to TI's attitude.<br />
<br />
<span style="font-size: large;"><b>Conclusion (Yeah about time too!)</b></span><br />
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://upload.wikimedia.org/wikipedia/commons/9/9c/Hp35s_Calculator.jpg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="400" src="http://upload.wikimedia.org/wikipedia/commons/9/9c/Hp35s_Calculator.jpg" width="220" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Hewlett-Packard<br />
HP-35S</td></tr>
</tbody></table>So, they are all useless? Well, useless is probably putting it a bit strongly, but I am disappointed that calculators haven't evolved more. The processor power available from ARM chips is hardly being used at all.<br />
<br />
I am tempted to buy a Hewlett Packard HP-35S. It is made by Kinpo (urgh) and the OS is seriously buggy - to the point that the OS can crash, or erroneous results can be generated. But it looks a much more professional than anything else on the market. Come on Kinpo - sort it out! The HP-35S was brought out to commemorate the 35th anniversary of the original HP-35, but is the logical successor to the recent HP-33S. A calculator whose keys were angled in a V-shape, to look like - you guessed it - a mobile phone. It seems that someone at HP or Kinpo actually realised that professionals don't want their tools to look like a kids toy!<br />
<br />
Is it too much to hope that someone might perhaps produce a successor to the superb<a href="http://en.wikipedia.org/wiki/HP-41"> HP-41 series</a>? This calculator still has a huge amount of following, to the point that a number of emulators are available. Most notably, an <a href="http://www.alsoftiphone.com/i41CXplus/">emulator for the iPod/iPhone/iPad from Alsoft</a>. Not only does it fully emulate an HP-41CX (including printer) but they have added GNUplot functionality too. Best of all, it is priced at just £15. HP are asking £30 for their HP-35S emulator.<br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://www.alsoftiphone.com/i41CXplus/images/CASPlot.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><br />
</a></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><img border="0" height="256" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5h12eX4qiMccKhyZcnDBCiI8mb_qaIKzaOSMOFyOkjrUx3MqmNv6gsj1IFbByLpy1IZv0pwNKTsIUnV_OVPkQqFxfX0YQOU1PqBGZQYUN4BqGIVaoOY5lF4Tw2XT3EVAzWNyvTfuWyZeV/s400/i41.jpg" style="margin-left: auto; margin-right: auto;" width="400" /></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><a href="http://www.alsoftiphone.com/i41CXplus/">Alsoft's i41CX+</a></td></tr>
</tbody></table><div class="separator" style="clear: both; text-align: center;"></div><br />
Is this the future for calculators? I hope not. I would miss being able to turn on a physical calculator in a fraction of a second, and to receive direct feedback from the keys. I hope it will alert HP (and TI and Casio) to the untapped potential out there.<br />
<br />
I would love to hear from anyone out there who has an opinion on this. I guess I am merely on the fringes of calculator geek-dom, I know there are some real collectors out there who go to extreme measures to get just the right calculator with an early serial number, but to me they are primarily an important tool and it frustrates me that nobody seems to make the right one for me. <br />
<br />
<br />
</div><div class="MsoNormal"></div>Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com12tag:blogger.com,1999:blog-3933619678696660447.post-54127875447831547062011-05-17T21:51:00.000+01:002011-05-17T21:51:46.414+01:00Precision Current Measurement<div style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: large;"><b>Building the Perfect <strike>Beast</strike> Current Meter</b></span></div><div style="font-family: Arial,Helvetica,sans-serif;"><br />
</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><b style="mso-bidi-font-weight: normal;"></b></div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;">In order to measure resistance (and, for that matter, inductance and capacitance) we need to measure both the voltage across the device, and the current through it. The voltage part is easy, we drive the device at a known voltage derived from a precision source. Measuring current is a little trickier, especially when you are trying to do it with an AC source, as you must for an inductance, capacitance or LCR meter.<br />
<br />
The traditional way of measuring current is to introduce a small resistance into the circuit, and measure the voltage across it. Clearly, this voltage offset (sometimes known as burden voltage) is going to change the effective drive voltage, and will be a particularly large offset when the device under test (DUT) is comparatively low resistance. <br />
<br />
What we need to do is somehow re-inject this voltage drop back into the circuit, and - hey presto - no more burden voltage to distort readings. We could do this by feeding back the voltage from the current sensor and offsetting the drive level, but there is a much simpler way.<br />
<br />
Those of you who have studied electronics at school, college or university may remember the inverting configuration of the op-amp. Feedback is applied to the inverting (-) input, so that it is driven to the same potential as the non-inverting (+) input. This makes it appear that there is a zero-resistance short circuit between the inputs, but it is a very controlled one.<br />
<br />
Another name for the inverting input in this configuration is the “virtual ground”, but in practise it can be driven to any level within the op-amp’s spec (largely limited by the power supply rails). This can be very useful, as we can effectively offset the ground potential by applying a voltage to the non-inverting input instead of grounding it.</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRGrUEJQV_A5eJnaS3v8SC3JjIiypXsmqsq07PO2lxh9Ei7vg95IMw6Mix6IxMTKdaIhkDsE09rGSZzz6i8bGp0etKcNNqjPlwxCP4SeBY8TTosQo_8U_uAv9B-AKnSlQbXm0ntDw_UQWz/s1600/TransImpedanceAmplifier.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRGrUEJQV_A5eJnaS3v8SC3JjIiypXsmqsq07PO2lxh9Ei7vg95IMw6Mix6IxMTKdaIhkDsE09rGSZzz6i8bGp0etKcNNqjPlwxCP4SeBY8TTosQo_8U_uAv9B-AKnSlQbXm0ntDw_UQWz/s320/TransImpedanceAmplifier.png" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig.1</td></tr>
</tbody></table></div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;">If we introduce a resistor into the circuit as above, the op-amp will continue to do whatever it takes to make sure both inputs are at the same potential. Thus creating a potential difference across the resistor which is proportional to the current flowing through it. Handily, the DUT still thinks it has a near-zero impedance path to ground. Simply put:<br />
<br />
<b>V<span style="font-size: x-small;">out</span> = -I<span style="font-size: x-small;">in</span> * R<span style="font-size: x-small;">fb</span></b> <br />
<br />
</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: large;">Problems and Gotchas</span><br />
<br />
Clearly, the op-amp output has to be able to source and sink sufficient current, and the feedback resistor must be chosen so that the output voltage does not approach the supply rail voltages. Without a custom output drive stage, current is going to be limited to 100mA or so.<br />
<br />
Any system with negative feedback has the potential to oscillate, especially if the source is capacitive or inductive and so capable of inducing a phase change. The solution is to add capacitance in parallel with the feedback resistor, but this clearly limits the response bandwidth. Not a problem if the current being measured is DC, but potentially problematic in an AC system such as the LCR meter.<br />
<br />
Another less obvious problem is input bias current (I<sub>b</sub>). Any op-amp requires a small amount of current to be present at the inputs before the input stage transistors detect a signal. This is normally negligible, in the order of nA or even pA, but this may be an issue in certain ultra-sensitive current meter applications and should be borne in mind. Similarly, op-amp inputs have an offset voltage (V<sub>os</sub>) that may be problematic under extreme circumstances.</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><br />
<br />
</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: large;">Transimpedance / Transconductance Amplifier - What's the Difference?</span><b style="mso-bidi-font-weight: normal;"><br />
</b><br />
</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;">I can never remember which is which, so I had to look it up! Apologies if I get these wrong elsewhere! <span style="-moz-font-feature-settings: normal; -moz-font-language-override: normal; font-size-adjust: none; font-size: 7pt; font-stretch: normal; font-style: normal; font-variant: normal; font-weight: normal; line-height: normal;"> </span><br />
<br />
<ul><li>A <i>transimpedance </i>amplifier converts an input current to an output voltage.</li>
<li>A <i>transconductance </i>amplifier converts an input voltage to an output current.</li>
</ul></div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><br />
</div>Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com2tag:blogger.com,1999:blog-3933619678696660447.post-58170836272255182192011-04-22T21:03:00.000+01:002011-04-22T21:03:40.155+01:00PCB Fabrication - DIY or Commercial Services?(At the time of writing it is Good Friday, so a Biblical start seemed appropriate) <br />
<br />
In the beginning...<br />
<br />
Was tagstrip and perfboard, which begat Veroboard, and it was good. Then the 1980s came along, and lo! Hobbyists didst discover copper clad and ferric chloride etchant, and there was much rejoicing.<br />
<br />
I seem to remember my first printed circuit board used some of my mum's nail polish. Dalo pens then arrived in my toolbox, along with rub-down transfers, and my PCBs got a bit fancier.<br />
<br />
I think it was some time around 1990 that I graduated to photo-etch. This meant I could use proper CAD tools and high resolution printed transparencies. An entire new world had suddenly opened up to me! With surface mount devices starting to become popular, it meant that I could lash up relatively quick prototypes without having to post a floppy to a commercial PCB house (even in the late 90s many still didn't use the Internet), wait for them to do whatever they do, and eventually post me the completed board complete with an invoice that would make Bill Gates wince. <br />
<br />
Of course, self-made PCBs don't have through-plating (although in most instances there are work-arounds for this) and cannot normally be multi-layer, so that does limit what you can do, but for 1-off prototypes that don't have to be optimised for size and price (and indeed how they look) then self-made PCBs had a lot going for them.<br />
<br />
Another decade went by, the 21st century arrived and things moved on again. Eastern Europe and China started to increase their influence and using commercial PCB houses not only became financially viable, but effectively relegated the UV exposure unit and bubble etcher to the store room. Then the world economy fell off a cliff, taking the exchange rates with it. PCB prototyping services once again started to look painfully expensive.<br />
<br />
So, the market is changing once again. This time, the concept that is changing things, is that rather than selecting from the 200 dishes available on the restaurant menu, you can have a burger, or a quarter pounder burger. Companies like Itead are starting to fill that huge gap at the bottom of the market . In terms of bangs-per-buck they are great, but there obviously have to be compromises and limitations.<br />
<br />
Itead and SeeedStudio charge a fixed fee, for which you get 5x5cm or 10x10cm of dual layer, green solder mask to play with, and you receive 10 PCBs, 5 of which are tested. Personally, I would prefer just 1 tested PCB, but the actual production process costs peanuts, the money goes in set-up costs. It is thought that these companies use spare board capacity on large panels that are already being used for other PCBs. Places like DorkBot create efficiency by waiting until they have enough to make up a big batch run, hence the lack of selection of finishes.<br />
<br />
These processes don't have great tolerance (at $20 I wouldn't expect it anyway) and the size limitation can be a problem, but what are the options? <a href="http://digital-diy.com/General-Electronics/pcb-fabrication-sources.html">Jon Chandler over at Digital-DIY has compiled an excellent run-down of the various PCB suppliers here</a>. <br />
<br />
Having run my requirements through some of the web sites, there is a bit of a jump between the ultra low budget suppliers and the mainstream. For those times when 10x10cm isn't enough, and a fortnight turnaround is too long, I think I am going to give serious to consideration to dusting off the bubble etch tank and going back to making my own.<br />
<br />
Interestingly, Itead are now doing PCBs at 5x15cm and 10x15cm. Sadly, that's just 1cm short of Eurocard size, but nevertheless it is a good amount of PCB real estate.<br />
<br />
<br />
<span style="font-family: Arial,Helvetica,sans-serif; font-size: large;">PCB Houses</span><br />
<br />
<a href="http://www.seeedstudio.com/depot/">SeeedStudio. </a><br />
5x5cm (10 pcs) US$20 +$4 standard postage<br />
10x10cm (10 pcs) US$40 +$5 standard postage<br />
<br />
<a href="http://iteadstudio.com/store/index.php?main_page=index&cPath=19_20">Itead</a><br />
5x5cm (10 pcs) $12 <br />
10x10cm (10 pcs) $28<br />
Also now offering: <br />
5x15cm (10 pcs) $38<br />
10x15cm (5 pcs) $48<br />
<br />
<a href="http://dorkbotpdx.org/">BatchPCB</a><br />
<br />
<a href="http://dorkbotpdx.org/">Dorkbot</a><br />
<br />
<a href="http://www.pcbcart.com/">PCB Cart</a><br />
<br />
<a href="http://www.pcbfabexpress.com/">PCB Fab Express</a><br />
<br />
<a href="http://www.pcbgeek.com/">PCB Geek</a>Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-20886558118669165662011-04-12T18:12:00.001+01:002011-04-15T00:51:27.041+01:00Design for a Precision LCR meter - Part 2 - Design Tweaks<div style="font-family: inherit;"></div><div class="MsoNormal" style="font-family: inherit;"><u></u></div><div class="MsoNormal" style="font-family: inherit;">Before I start, I should say a big thanks to <a href="http://www.eevblog.com/">Dave Jones</a> and <a href="http://chrisgammell.com/">Chris Gammell</a> for giving this project a shout-out on the excellent <a href="http://www.theamphour.com/">AmpHour weekly podcast</a>. It sent my weekly reader stats up by a factor of 10! Cheers guys! </div><div class="MsoNormal" style="font-family: inherit;"><br />
</div><span style="font-family: inherit;"> </span><br />
<div class="MsoNormal" style="font-family: inherit;">A number of people have contacted me about the LCR meter project. It is really good to hear from other people and find out what they think and has certainly given me some food for thought. I have been asked if I will be publishing the full schematics and making a PCB available. I will certainly be making the schematics and Gerbers available in a downloadable CAD file (probably Altium format). I <i>may </i>make a small number of prototype PCBs available if there are no bugs. I do not intend to sell any kits or complete products. </div><div class="MsoNormal" style="font-family: inherit;"><br />
<div style="font-family: Arial,Helvetica,sans-serif;"><b><span style="font-size: large;">Not Design for Manufacture - Design for Me</span></b></div><br />
</div><div class="MsoNormal" style="font-family: inherit;">It is worth me saying a few words about the general design of the LCR meter. Most designs have a target customer in mind. This might typically be a hobbyist kit constructor or a commercial product manufacturer. In this instance, the target customer is just me. This means that, in the first instance, I am designing around what is cheapest and most effective for myself. I have an FTDI USB module in my spares boxes, along with an <a href="http://www.analog.com/en/rfif-components/direct-digital-synthesis-dds/ad5933/products/product.html">AD5933</a>, <a href="http://www.analog.com/en/rfif-components/direct-digital-synthesis-dds/ad9834/products/product.html">AD9834 DDS</a> and <a href="http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en549052">PIC16LF1518</a>. </div><div class="MsoNormal" style="font-family: inherit;"><br />
</div><div class="MsoNormal" style="font-family: inherit;">If I were optimising this for minimum production cost, I would remove the DDS, multiplexers and PIC16. I would swap the controller for a PIC18 or ARM (anything cheap with USB capability and lots of I/O pins) and would replace the multiplexers with nice cheap 2-to-4, 3-to-8 or 4-to-16 logic decoders and MOSFETs acting as switches. Something along these lines:</div><div class="MsoNormal" style="font-family: inherit;"> </div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/Blogger/BudgetRangeSelector.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="292" src="http://i222.photobucket.com/albums/dd237/Zadpics/Blogger/BudgetRangeSelector.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig.1: Alternative inexpensive range select circuit</td></tr>
</tbody></table><div class="MsoNormal" style="font-family: inherit;"><br />
</div><div class="MsoNormal" style="font-family: inherit;">The DDS would be replaced with a chain of dividers with some more MOSFETs to select the appropriate frequency division ratio. With sufficient free I/O pins, the binary decoders could probably be removed from the design too. </div><div class="MsoNormal" style="font-family: inherit;"><br />
</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/Blogger/BudgetProgrammableClockSource.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="202" src="http://i222.photobucket.com/albums/dd237/Zadpics/Blogger/BudgetProgrammableClockSource.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig.2: Alternative programmable clock source</td><td class="tr-caption" style="text-align: center;"><br />
</td></tr>
</tbody></table><div class="MsoNormal" style="font-family: inherit;"><br />
</div><div class="MsoNormal" style="font-family: inherit;"></div><div class="MsoNormal" style="font-family: inherit;">The most important thing I would add would be some protection against charged capacitors! I don’t measure big high voltage caps, but you can be sure that there would be users out there who would forget, and then blame me for not protecting their meter (and computer!). I guess I could add passive protection via some zeners on the sense connections, but I am not sure how big these would need to be to cope with a fairly meaty cap discharges whilst still protecting the meter. </div><div class="MsoNormal" style="font-family: inherit;"><br />
</div><div class="MsoNormal" style="font-family: inherit;">An alternative would be a relay either isolating the meter, or acting as a crowbar across the measurement terminals. Relays do draw a relatively high amount of current though, reducing lifespan on battery powered devices, and can tend to oxidise over time, leading to intermittent contact.<br />
<br />
If I were going to the extent of putting a relatively 32-bit ARM controller in there, that would open up the possibility of making it hand held, or at least a standalone portable. As it is, there will be a connector for a standard 4x20 LCD and a keypad, but they are there mostly for debugging. I have no requirement for a portable meter and that add another set of constraints that would push up both the development time and cost.</div><div class="MsoNormal" style="font-family: inherit;"><br />
</div><div class="MsoNormal" style="font-family: inherit;"><div style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: large;"><b>Range Selection </b></span></div><u><br />
</u></div><div class="MsoNormal" style="font-family: inherit;">You may recall from Part 1 that I am using two switched ranges to maximise the LCR meter's measurement range. The first of these controls the voltage across the Device Under Test (DUT), the second range selects the amount of gain generated by the I-V amplifier.<br />
<br />
I selected the <a href="http://www.analog.com/">Analog Devices</a> <a href="http://www.analog.com/en/switchesmultiplexers/multiplexers-muxes/adg706/products/product.html">ADG706 </a><a href="http://www.analog.com/en/switchesmultiplexers/multiplexers-muxes/adg706/products/product.html">16-channel analogue multiplexer</a> for this task. 16 channels may seem somewhat over the top, but it is nice to have extra space to be able to experiment. I may well be using 10 or so gain settings in the receive amplifier anyway, so a 16 channel switch is ideal. </div><div class="MsoNormal" style="font-family: inherit;"><br />
It is crucial that the multiplexer does not have a high “on” resistance, which would potentially affect the net value of the lowest feedback resistor (possibly as low as 100 Ohms). I have seen multiplexers with an “on” resistance as low as 0.5 Ohms, but these only appear to be 4 channels at best. The <a href="http://www.analog.com/en/switchesmultiplexers/multiplexers-muxes/adg706/products/product.html">ADG706 </a>has a usefully low “on” resistance of 2.5 Ohms which is pretty decent. Channel crosstalk capacitance and resistance figures seem to be sufficient too, but that will need testing to be sure.</div><div class="MsoNormal" style="font-family: inherit;"><br />
<div style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: large;"><b>Drive Amplifier</b></span></div></div><div class="MsoNormal" style="font-family: inherit;"><br />
As it stands, the <a href="http://www.analog.com/en/rfif-components/direct-digital-synthesis-dds/ad5933/products/product.html">AD5933 </a>is only designed to measure down to 1kOhms. At impedances below this, the drive amplifier cannot supply sufficient current. Whilst the AD5933 has a number of pre-set drive ranges, the manufacturer’s data sheet for the AD5933 advises the use of an external amplifier (actually acting as an active attenuator). They suggest using one of the following op-amps: <a href="http://www.analog.com/en/amplifiers-and-comparators/operational-amplifiers-op-amps/ad8531/products/product.html">AD8531</a>, AD820, AD8641, AD8627. Comparing data, the <a href="http://www.analog.com/en/amplifiers-and-comparators/operational-amplifiers-op-amps/ad8531/products/product.html">AD8531 </a>can drive the most current (+/- 250mA) and has the best capacitance driving ability (100nF @ 300kHz). Happily, it is also the cheapest one suggested.<br />
<br />
100nF doesn’t seem a very high maximum capacitance, but in practise we don’t need the amplifier’s full performance. If we consider that a 100nF capacitor at 100kHz has an impedance of just 15.9 Ohms then we should be driving it at a lower peak-to-peak voltage, and at a lower frequency. Both of which greatly improve the chip's ability to drive capacitive loads beyond the headline spec. Although I do want to retain the ability to sweep as high a frequency range as possible, in order to detect potential resonances. This means that rather than driving the DUT at a standard 3V pk-pk we need to be looking at sub-mV level capability.<br />
<br />
Stability at high capacitances and various drive frequencies needs to be tested. Unfortunately SPICE simulations aren't great at modelling this sort of thing.</div><div class="MsoNormal" style="font-family: inherit;"><br />
<a href="http://www.analog.com/en/rfif-components/direct-digital-synthesis-dds/ad5933/products/product.html">(Reference AD5933 Data sheet Rev. C p.31)</a></div><div class="MsoNormal" style="font-family: inherit;"><br />
</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: large;"><b>Drive Offset</b></span></div><div class="MsoNormal" style="font-family: inherit;"><br />
The AD5933 is a single-supply chip, and so generates a sinusoidal test signal which is biased by a DC offset. Normally this is not a problem as the receive amplifier simply subtracts the same amount. Curiously, the data sheet claims the output offset (for a 3.3V input) to be 1.48V, yet it shows the receive amplifier biasing the remote end of the DUT at Vdd/2 (1.65V). The recommended drive amplifier circuit also adds Vdd/2 to the existing offset. To confuse matters further, the AD5933 can also be programmed to drive at various pk-pk levels with a different offset. It may be easier to ignore this facility and rely on my own gain and offset control.<br />
<br />
The design suggested in the data sheet clearly has the potential to generate a DC bias voltage (1.65V-1.48V=0.17V) which would manifest itself as an unwanted current in any inductor or resistor being measured. This would normally be calibrated out, but as we intend to measure relatively low values (and so generate small stimulus signals), the offset may swamp the intended signal and may generate a dangerously high current in low resistance DUTs. A trim pot would probably suffice if we were just using a fixed gain in the drive amplifier, but there is another possibility:</div><div class="MsoNormal" style="font-family: inherit;"><br />
<div style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: large;"><b>Programmable DC Bias Correction</b></span></div></div><div class="MsoNormal" style="font-family: inherit;"><br />
Rather than using a fixed offset correction, how about using a small, low resolution DAC to set the null? This allows the unit to self-correct an offset which may drift according to gain and temperature, but it also allows us to superimpose the AC on top of a known DC bias if we so choose. The actual capacitance of many capacitors does change with voltage (many engineers are unaware of this) and it may prove useful to be able to test values with a bias voltage (or current in the case of inductors) even if it is only a modest +/- 1V or less.</div><div class="MsoNormal" style="font-family: inherit;"><br />
</div><div class="MsoNormal" style="font-family: inherit;"><br />
</div><div class="MsoNormal" style="font-family: inherit;"><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/Blogger/TXDriveBuffer.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="270" src="http://i222.photobucket.com/albums/dd237/Zadpics/Blogger/TXDriveBuffer.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig.3: Drive Buffer - Programmable AC Gain and DC Offset Trim</td><td class="tr-caption" style="text-align: center;"><br />
</td></tr>
</tbody></table><br />
</div><div class="MsoNormal" style="font-family: inherit;">The 20 Ohms resistor output on the op-amp output is recommended in the application note. The AD8531 has a low impedance drive and is capable of sourcing and sinking 250mA. Accidentally going beyond this may result in damage, so a current limiting resistor is a sensible addition. It also helps to protect against the user attempting to test a charged capacitor.<br />
<br />
<br />
<span style="font-family: Arial,Helvetica,sans-serif; font-size: large;"><b>Enclosure and Measurement Probes</b></span><br />
<br />
</div><div class="MsoNormal" style="font-family: inherit;">What I haven’t yet decided is how I am going to connect the devices under test. This will in turn dictate how the meter is housed. A quick way of measuring surface mount devices might be to have a small PCB with a line etched down the middle, and a plastic mask over the top that holds the DUT in the correct position. That really means somehow obtaining a gold plated PCB though, unless I can find something to cannibalise for the job – maybe gold plated connector fingers. It all feels a bit too much like a rough-and-ready hack, which I want to avoid.Through-hole components will be tested via conventional test probes with standard 4mm banana connectors. Most test tweezers have standard banana plugs, which is useful, but I would rather have a hands-free test ability for small capacitances and inductances. Perhaps an external test fixture would be the best way.</div><div class="MsoNormal" style="font-family: inherit;"><br />
</div><div class="MsoNormal" style="font-family: inherit;">That is pretty much where things are at right now. I have started schematic entry, but this new installation of Altium is being a pain. I really need a few hours together to concentrate on this beastie.<br />
<br />
As ever, feel free to leave comments, it is always good to hear opinions and good ideas. See you in part three!<br />
<br />
<br />
</div>Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com4tag:blogger.com,1999:blog-3933619678696660447.post-87598980372507607892011-04-11T23:33:00.000+01:002011-04-15T00:51:45.787+01:00*Sigh* - Work, Employment Agencies and CVs / Resumés - A Little Advice(Note to non-British English speakers, C.V. = Resumé)<br />
<br />
Before I start, part two of the precision LCR meter will be along shortly. It is all written up, but still needs a couple more diagrams drawing. What can I say, the weather here in the UK at the weekend was absolutely glorious; sunny and warm, with all the spring flowers out. After a long and miserable winter I didn't feel like staying inside and doing computer things. Sometimes even the most techy of engineers has to take a step back and spend some time being an analogue human being.<br />
<br />
<b style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: large;">Don't You Just Love Employment Agencies?</span></b><br />
<br />
Anyway, here we are. Another Monday, another annoying employment agency. Actually no, just the same employment agency, <i>again</i>. To recap, a few weeks ago I received a phone call from an employment agency who had seen my business details in a trade directory (<a href="http://www.electronicsyorkshire.org.uk/">Electronics Yorkshire</a>) and wanted to know if I was recruiting. I said that I was not, as my business consists mostly of me, with the occasional assistance of some trusted hardware and software people that I have known a long time. After hearing this, they couldn't get off the phone quickly enough, but were very polite about it. So far so good.<br />
<br />
A couple of days later I received an email from the aforementioned agency, with an attached CV. To be fair, the email did say "If this candidate is not relevant to you, please let me know and I will amend your details" so I emailed them back, explained that I was not recruiting and would they please stop sending me unsolicited personal information. I don't think it is fair on the candidates that their information should be shown to complete strangers, and to people who could potentially be their current employer. Even with basic personal details redacted, it isn't that difficult to tell who they are if they currently work for you.<br />
<br />
Just four days later, I got yet another email with the title "AVAILABLE ELECTRONICS ENGINEER" (I do find that titles in all capitals <i>really </i>help, don't you?). Despite redactions, after 30 seconds on Google I had the candidate's name. 4 minutes and I had his address. The power of the Internet is scary sometimes. Unfortunately not powerful enough to supply me with an email address for the engineer concerned or I would have let him know what his agency were doing with his personal information. Would a paper snail mail be over the top? Probably. I think most engineers are cynics anyway, and rarely amazed by what agencies get up to.<br />
<br />
Today I received a third CV from them - entitled "Available Embedded Software Engineer". Sounds like they are diversifying, I wonder how long before they are sending CVs from Control Systems and HVAC engineers. Still, "know your enemy" is a useful maxim, and it is always good to see what the competition are offering, so I thought I should have a look at it. I'm glad I did. If these CVs are anything to go by, I am seriously under-valuing my skills. I am also nowhere near as good at spouting bulls**t as I should be. Yes, I can tell this surprises you.<br />
<br />
Like most people, I hate writing my CV and am never totally sure what to put in and leave out. There seem to be as many "correct" ways to do it as there are employers. Even so, I was amazed at the quality of this particular CV. Or the lack of it. So amazed that I thought I should blog about it; partly to amuse and partly to show younger engineers and students what they shouldn't be doing.<br />
<br />
<br />
<div style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: large;"><b>Writing Your CV - Some Advice.</b></span></div><br />
First things first. Four pages is way too long for a CV. Two or maybe three pages is plenty to get across the bare bones if your history. Details can be given on additional sheets if you need to, or on a <u>password secured</u> web page. This way you can make your relevant details available live, and you can ensure that they are up to date. Any sample documentation or photos of your work is a bonus, but don't put it in your CV.<br />
<br />
<div style="font-family: Arial,Helvetica,sans-serif;"><b>Get someone to proof-read your CV. </b></div><br />
There will be spelling and grammar mistakes in your CV that your eyes just don't see, just like there are in this blog. If you are dyslexic (and many creative people are), or English is not your native language, then there is no excuse for not getting someone to check it over for you. You would really hope that a good employment agent would check it over too. A CV is a hugely important document which exists to get you an interview and it is representing you as a person, so check your personal statement particularly carefully. For example, do not write the following: <br />
<br />
<blockquote style="font-family: "Courier New",Courier,monospace;"><span style="font-size: x-small;"><span style="font-size: small;">"I am <span style="color: red;">(a)</span> very determined and enthusiastic individual with <span style="color: red;">(a)</span> very <span style="color: red;"></span>clear understanding of my <strike style="color: black;">future </strike>goals. I would like to <strike style="color: black;">peruse </strike><span style="color: red;">(pursue)</span> my career with a company which will give me early responsibility and is committed to staff training. I have a firm <strike style="color: black;">believe</strike> <span style="color: red;">belief </span>in myself and my abilities to meet any challenge as my career progresses <strike style="color: black;">forward</strike>."</span></span></blockquote><div style="font-family: "Courier New",Courier,monospace;"></div><br />
<div style="font-family: inherit;"><span style="font-size: small;">Sorry about getting all schoolteachery there - the red text and strike-thoughs are my additions. Yes, this is from the CV I was sent today; 6 mistakes in 55 words, half of them in the first sentence. A 31 year old engineer who doesn't know the difference between peruse and pursue, or believe and belief, and is asking for </span><span style="font-family: inherit; font-size: small;"><i>"Between £34,500 and £37,000 (negotiable)"</i>. It is hardly surprising though, most agencies don't seem to know the difference between principal and principle. If you don't know why I have corrected "future goals" and "progresses forward" then you should read up on <a href="http://en.wikipedia.org/wiki/Tautology_%28rhetoric%29">tautologies</a>.</span><!--[if gte mso 9]><xml> <o:OfficeDocumentSettings> <o:RelyOnVML/> <o:AllowPNG/> <o:TargetScreenSize>800x600</o:TargetScreenSize> </o:OfficeDocumentSettings> </xml><![endif]--><!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:TrackMoves/> <w:TrackFormatting/> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:DoNotPromoteQF/> <w:LidThemeOther>EN-GB</w:LidThemeOther> <w:LidThemeAsian>X-NONE</w:LidThemeAsian> <w:LidThemeComplexScript>X-NONE</w:LidThemeComplexScript> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> <w:SplitPgBreakAndParaMark/> <w:EnableOpenTypeKerning/> <w:DontFlipMirrorIndents/> <w:OverrideTableStyleHps/> </w:Compatibility> <m:mathPr> <m:mathFont m:val="Cambria Math"/> <m:brkBin m:val="before"/> <m:brkBinSub m:val="--"/> <m:smallFrac m:val="off"/> <m:dispDef/> <m:lMargin m:val="0"/> <m:rMargin m:val="0"/> <m:defJc m:val="centerGroup"/> <m:wrapIndent m:val="1440"/> <m:intLim m:val="subSup"/> <m:naryLim m:val="undOvr"/> </m:mathPr></w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" DefUnhideWhenUsed="true"
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</div><div style="font-family: inherit;"><span style="font-size: small;"><span>A word about the content: at 31 you are also no longer a fresh graduate, and responsibility at that age is not "early". Good luck finding a company with staff training. Most tech departments now are quite small and don't have any formal training.</span></span></div><div style="font-family: inherit;"><span style="font-size: small;"><br />
</span></div><div style="font-family: inherit;"><span style="font-size: small;"><br />
</span></div><div style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: large;"><b>It is not what you write that matters, but what you leave out.</b></span></div><br />
<b>Part 1: Experience</b><br />
<br />
This works in two ways. First of all, employers are really not interested in what you did for a few hours once. If you are getting a job based on a small amount of experience then you will get found out quickly anyway. Cut to the chase and tell them what you can do well. Secondly, <u>don't</u> tell them what you are bad at! I'm not going to quote the poor sod's CV here there is no point. Briefly:-<br />
<br />
18 lines of "IT/computing and technical skills" (is there a difference?) of which 4 skills are described as "basic" level. In a list that big, those 4 can comfortably be dropped. Otherwise it drags down your perceived average. What are you good at? I mean <i>really </i>good, not just something you did for a week or so. Being able to wire an RS232c lead is not an outstanding engineering skill.<br />
<br />
28 lines of text describing what you did for 3 years at one particular company, many of which are describing the same thing in a different way. I lost the will to live after 5 lines (hey, reader, if you made it this far then well done!) <br />
<br />
The more specialist your skills are, the less you should need to write in your list. Target them at whatever role you are applying for too. If you make your lists hard work then your CV will get binned in no time.<br />
<br />
<div style="font-family: inherit;"><b><span style="font-size: small;">Part 2: Qualifications</span></b></div><div style="font-family: inherit;"><span style="font-size: small;"><br />
</span></div><div style="font-family: inherit;"><span style="font-size: small;">What matters most to any employer is what you are <u>now</u> and what you can do. A word to Mr Anonymous-CV-Owner: When I saw the marks for <i>every single chuffing test </i>you have done in 4 years of University </span><span style="font-size: small;">(yes, he really did, all 34 of them),</span><span style="font-size: small;"> I did rather wonder how the University of Bradford managed to award a 2:1.</span></div><div style="font-family: inherit;"><br />
</div><div style="font-family: inherit;"><span style="font-size: small;">Now, there are some decent scores in there, mostly in the mid 60s, with a couple in the 80s, but what my brain sees are these:</span></div><blockquote><div style="font-family: inherit;"><!--[if gte mso 9]><xml> <o:OfficeDocumentSettings> <o:RelyOnVML/> <o:AllowPNG/> <o:TargetScreenSize>800x600</o:TargetScreenSize> </o:OfficeDocumentSettings> </xml><![endif]--><!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:TrackMoves/> <w:TrackFormatting/> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:DoNotPromoteQF/> <w:LidThemeOther>EN-GB</w:LidThemeOther> <w:LidThemeAsian>X-NONE</w:LidThemeAsian> <w:LidThemeComplexScript>X-NONE</w:LidThemeComplexScript> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> <w:SplitPgBreakAndParaMark/> <w:EnableOpenTypeKerning/> <w:DontFlipMirrorIndents/> <w:OverrideTableStyleHps/> </w:Compatibility> <m:mathPr> <m:mathFont m:val="Cambria Math"/> <m:brkBin m:val="before"/> <m:brkBinSub m:val="--"/> <m:smallFrac m:val="off"/> <m:dispDef/> <m:lMargin m:val="0"/> <m:rMargin m:val="0"/> <m:defJc m:val="centerGroup"/> <m:wrapIndent m:val="1440"/> <m:intLim m:val="subSup"/> <m:naryLim m:val="undOvr"/> </m:mathPr></w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" DefUnhideWhenUsed="true"
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</style> <![endif]--> </div><div style="font-family: "Courier New",Courier,monospace;"><span style="font-size: small;"><span>Radio Transmission and Reception <span></span>40%</span></span></div><div style="font-family: "Courier New",Courier,monospace;"><span style="font-size: small;"><span>Signal and Systems Theory <span></span>47%</span> </span></div><div style="font-family: "Courier New",Courier,monospace;"><span style="font-size: small;"><span>Financial Management<span> </span>45%<span> </span></span></span></div><div style="font-family: "Courier New",Courier,monospace;"><span style="font-size: small;"><span><span></span>Embedded Systems<span> </span>45% </span></span> </div><div class="MsoNormal" style="font-family: "Courier New",Courier,monospace;"><span style="font-size: small;"><span></span>Analogue Electronics 1<span> </span>48%</span></div></blockquote><span style="font-size: small;"><span style="font-family: "Arial","sans-serif";"></span> </span>See where I am going here? You got a 2:1 and my brain is seeing just-scraped-by marks, especially the one in embedded systems - and you are applying for an embedded software job. The thing is, most of us have marks like that! I have never, ever, been asked for my individual test marks. Which is probably a good thing, because I have no idea where they are. So don't tell them! Instead, just say you have a 2:1 B.Eng. Honours. and an M.Sc. If they want details then supply them, but not until then.<br />
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<div style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: large;"><b>The Elephant In The Room</b></span></div><br />
I was once in an interview (oddly enough with a company that was a spinoff of our hero's University) when the interviewer said a surprising thing. He said I should always attach a photograph with my CV. I asked why. In not so many words, he said it was because I was 6ft tall, slim and, quite frankly, white. He didn't say white, but he used many many words to avoid saying so. Ever since then I have declined to add a photograph to my CV. I know this is probably strange coming from an Anglo-Saxon white male in Middle England, but I want to be judged on my abilities not my skin colour.<br />
<br />
Our hero lists his under-16 education as a Foundation College in Pakistan. With the best will in the world, that could be the Eton or Harrow of Pakistan and I wouldn't have a clue. However good they are, you can be pretty sure that any employer will not rate it as highly as UK GCSEs, and it is going to be very difficult to verify your marks.With a Masters Degree and experience under your belt, I would only add details of my pre-16 education if I got stunning results in the locally accepted examination system.<br />
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Under "Additional Skills, Activities and Interests", he also lists Languages: Urdu and Punjabi (Fluent-native). This does partially explain the standard of English (although not why it wasn't checked), but why include it unless you know it is necessary for the job? Why not list English too? Don't give the person filtering out CVs any excuse to be in any way racist. Don't pretend to be something you aren't, but instead persuade them to concentrate on being able to do the job.<br />
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<span style="font-size: large;"><b><span style="font-family: Arial,Helvetica,sans-serif;">What It All Boils Down To</span></b></span><br />
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Remember, when applying for a job, of all the people you come into contact with, only <u>one</u> has the power to say yes. All the rest are there to say no. Give them as few reasons as possible to filter you out. <br />
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<span style="font-size: large;"><b><span style="font-family: Arial,Helvetica,sans-serif;">Oh, Just One More Thing...</span></b></span><br />
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If you are an employer or an engineer looking for work in the UK, the name of this agency is Progressive Recruitment, based in Manchester. Use your own judgement as to their standards, just consider that they don't read emails, and that they send out personal CVs to people who haven't requested them.Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-7941001488369034112011-03-30T16:22:00.001+01:002011-03-30T16:24:15.891+01:00The Amp Hour #36 — Big Business BuffooneryThe Amp Hour podcast is essential listening for anyone interested in electronics. Dave Jones, Chris Gammell (and occasional guests) have a chat and a rant about life, the universe and electronics. Well, mainly electronics if I'm being honest. Great entertainment for the drive to work, or something to listen to rather than the bloke at the next desk. Unless you work in Ohio or Sydney, in which case one of them might well be the bloke at the next desk!<br />
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Yeah, they might possibly have mentioned my LCR meter project too. Cheers guys!<br />
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<a href="http://www.theamphour.com/" title="The Amp Hour"><img alt="The Amp Hour" src="http://www.theamphour.com/wp-content/uploads/2010/08/TheAmpHourLogo_150.png" title="The Amp Hour" /></a>Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-60408002604362295652011-03-23T01:21:00.001+00:002011-03-23T02:08:37.608+00:00Design for a Precision LCR meter (AKA: Prospero Gets a Brother) - Part 1<div class="MsoNormal">I suppose this project should really be called Antonio as it is the brother of Prospero, but it doesn’t exactly sound right for a piece of test equipment. An appropriate name evades me for the moment. It is probably just as well.</div><div class="MsoNormal"><br />
</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><span style="font-size: small;"><b>Measuring Inductance, Capacitance and Resistance. </b></span></div><div class="MsoNormal"></div><div class="MsoNormal">In designing Prospero (the RF vector network analyser) it has come to my attention that the inductance and capacitance measuring equipment currently available to me isn’t exactly precision lab reference grade. A resolution of 1nF isn’t really good enough when you are working at sub-pF level. Upon investigating, it seems that a basic LCR (Inductance, Capacitance, Resistance) meter starts at around £150. If I want to measure the equivalent series resistance (and I do) then I am looking at upwards of £250. Hmm. I don’t really have that sort of money to spend on another meter, so just <i>what</i> is an engineer to do? </div><div class="MsoNormal"><br />
</div><div class="MsoNormal">Well, after an amount of thought (somewhat less than a second), I decided that building my own was probably the best way forward. But then you knew that didn’t you! </div><div class="MsoNormal"><br />
</div><div class="MsoNormal">So, what architecture? There are plenty of simple embedded micro based meter designs around, but they are all designed around similar methods and are rather limited in range and accuracy. I had specified that the unit be capable of a test frequency of at least 100kHz and most units seem to stop at 10kHz. That inherently reduces the ability to read small value components with a good degree of accuracy. I remembered that a few years ago I was sent a sample of Analog Devices’ <a href="http://www.analog.com/en/rfif-components/direct-digital-synthesis-dds/ad5933/products/product.html">AD5933 1MSPS 12-bit Impedance Converter</a>. I had meant to do something with it, but it has certain limitations (which I will go into later) and at that time I was working in a lab which had nice test gear, so the chip got filed away. After a good read through of the data sheet however, I decided the AD5933 would probably take a lot of leg work out of my design and was good enough for my purposes.</div><div class="MsoNormal"><br />
</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/Blogger/AD5933.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="101" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiyr_LyRf0cZECSJCciCDuYYZnk-J2hu6YN6MSe6gVZiOCnbTPF5ym7aOT7O9tGC9jSvgSCXYLUKESmrMTfXpvuVblcrStvZT_okmN7Kvjf5F4mfpLXjYlOGJodUmovhoQPn5B7kmuFtcRZ/s400/AD5933.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/Blogger/AD5933.png"><span style="font-size: x-small;">Fig.1 AD5933 Impedance Converter - Simplified Block Diagram</span></a></td></tr>
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</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><b>Never Satisfied</b></div><div class="MsoNormal"></div><div class="MsoNormal">As I mentioned, the AD5933 isn’t perfect. The 10-bit DAC generates spurious signals outside the desired band (although the LPF filters many of these out in the receive section) it is inherently very poor at measuring low impedance values, and the maximum text frequency is limited to 100kHz. Ideally I would have liked 1, 10 or even 100MHz available to test RF components. So I set to work to design something of my own. The first result is reproduced below. </div><div class="MsoNormal"><br />
</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/Blogger/Improved-LCR-Meter.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="253" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgKqTwQ3vJ0h1puS3SZd0AtklmR7kLDuAy7DGEKOUPoiR7KCg0KjfGTCgI2S0Arp6isIhqIM4Upr1CKPjiZkE8fMCrLwLBGw9uH7ocU3QrST81_1OnSM9ZCExdYiO3OV2iH2SvO571uW1AG/s400/Improved-LCR-Meter.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/Blogger/Improved-LCR-Meter.png">Fig.2 Improved LCR Meter Design - Block Diagram</a></td></tr>
</tbody></table><div class="MsoNormal"><br />
</div><div class="MsoNormal">The intention was to DDS generate a clean 24-bit sinusoidal signal in software (probably with an ARM Cortex M3) and do the D-A conversion with a fancy hi-fi chip (they really are absurdly cheap). They can be pushed to well over 200KSPS, giving a precise and clean 100kHz source with only a little filtering. Simultaneous measurement of the current and voltage components is to be done with another 24-bit 200KSPS+ hi-fi ADC chip and streamed into the processor via DMA.</div><div class="MsoNormal"><br />
</div><div class="MsoNormal">To give flexibility, the output is capable of driving peak-to-peak levels between 0.01V and 10V at up to 10mA, with programmable offset. Voltage is sampled across the test ‘probes’ in a 4-terminal manner, with a set of programmable gains to ensure the best possible use of the ADC’s dynamic range. Current is measured via a transconductance amplifier (again with programmable gain) which produces a voltage proportional to the current through it, but without the ‘burden voltage’ associated with a simple resistor as used in most current measurement. This is then presented to the second ADC channel. After grabbing a large enough sample, software performs a simple Fourier conversion to the frequency domain. Comparing phase and magnitude gives us our desired parameters.</div><div class="MsoNormal"><br />
</div><div class="MsoNormal" style="font-family: Arial,Helvetica,sans-serif;"><b>However…</b></div><div class="MsoNormal"><br />
</div><div class="MsoNormal">In one of those moments to which most engineers are prone, I decided that wasn’t enough. I really needed 1/10/100MHz and had 14-bit 400MSPS DDS chips in stock. I could use one signal as a source, and a second (coherent) signal to compare the phase in a mixer, reading the magnitude in an ADC. Excellent. </div><div class="MsoNormal">One slight problem though. What I have actually described there is a network analyser. Basically it is a cut down version of Prospero, limiting at 100MHz instead of 500MHz, and not being able to measure the reflected signal. So what is the point making it when I will have a better tool in my hands before long? None at all! Sigh. I had gone around in a huge circle.</div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b style="font-family: Arial,Helvetica,sans-serif;">Back To The Beginning!</b> </div><div class="MsoNormal"><br />
</div><div class="MsoNormal">Anyway, I decided to go back to the start and go with the original AD5933 design. It can be modified to handle low impedance values, and the addition of a cheap external DDS makes the clock scale down to audio frequencies, which is handy for audio components such as loudspeakers etc. As you can see from the diagram below, the current sense gain will be selectable.</div><div class="MsoNormal"><br />
</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/Blogger/LCRMeter2.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="235" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEii3nJGgTmUtjO8ebgiSGbgB8bA_ERpngGq1RS4l_OUZPOADyVY2jIKFFyEUPWGbrGpwvQQUPX0Dbp1-8JDzM488BceNNc_HSqSP-f0tXbs-ogjktgdyd_h6u3o4FBEWnj2U0cn2fMck5wE/s400/LCRMeter2.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><a href="http://i222.photobucket.com/albums/dd237/Zadpics/Blogger/LCRMeter2.png">Fig.3 LCR Meter Block Diagram - Excluding Low Impedance Adaptor</a></td></tr>
</tbody></table><div class="separator" style="clear: both; text-align: center;"></div><div class="MsoNormal"><br />
</div><div class="MsoNormal">Control is to be done via a simple PIC16, with connection to the PC via an FTDI USB module. In theory I could probably bit-bang the operation from the FTDI module, but that would probably end up being more expensive and more complex than a cheap and fast PIC16. With an on-board micro, I could build in an LCD and do all the maths on the embedded micro but, to be honest, it isn’t going to move outside the lab, and it is far easier to do more exotic maths on a nice fast PC with a good display. Nevertheless, I will probably provide the appropriate connections to drive a standard LCD text module.</div><div class="MsoNormal"><br />
</div><div class="MsoNormal">For the moment, it is my intention to derive power from the USB connection. The entire system is low power, with the AD5933 drawing a nominal 10mA at 3V. Dropping from 5V to 3V also gives me the opportunity to provide more precise voltage regulation than USB gives, and also the ability to remove noise on the power lines, both of which improve the accuracy of the system. </div><div class="MsoNormal"><br />
</div><div class="MsoNormal">In Part 2 I intend to cover the design of the low impedance adaptor, how the current range is selected, and some ideas on how the system accuracy can be improved beyond the 0.5% claimed for the AD5933. Until then, toodlepip!</div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><br />
</div>Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com4tag:blogger.com,1999:blog-3933619678696660447.post-59899987836344131862011-03-17T19:43:00.001+00:002011-03-17T19:44:18.430+00:00The Brotherhood (and Sisterhood) of EngineersI have an awful lot of updates to write; The designs of Prospero and Miranda (Vector Network Analyser and JTAG programmer respectively) are coming on nicely, and there is a huge amount to say. But I am not going to, at least not yet. There are much more important issues I need to speak about.<br />
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Japan. One week on and things are at least starting to be a little clearer, but the media are largely still hysterical and uninformed. Even respected sources such as the BBC, CNN and New York Times are having trouble getting good quality information. For example, the BBC was presenting the loss of coolant in the used fuel storage tank as "current" more than 18 hours after the event. Media outlets are even copying things off each other, ending up with a strange sort of echoing feedback loop. Instead of reporting the known facts, they are falling back on the old method of wheeling in some supposed expert or other, who is then made to hypothesise what may be happening. The Japanese broadcaster NHK is not massively better, but at least seems to have faster access to what facts there are. You can currently stream NHK here via Ustream: <a href="http://www.ustream.tv/channel/nhk-world-tv">http://www.ustream.tv/channel/nhk-world-tv</a> . Their main fault is not displaying a "repeat" caption on video that might be an hour or two old, giving the impression that it is live. <br />
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Enough complaining though. I do not propose to cover the horrendous humanitarian situation. Far better people than I have written about it, and anything I could add would be pointless. You have seen the photographs and the news footage, they all speak louder than words.<br />
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My first comment is what happened in Tokyo. Or rather, what didn't happen in Tokyo. I don't know for sure what the earthquake measured in the city centre, it would be considerably less than the 9.0 at the epicentre, but still up around the 7.8 level. Beyond what they were theoretically designed to withstand.<br />
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If you are an engineer (of whatever discipline) you will know that engineers share that intangible "something". Whether you are in electronics, automotive, structural or civil engineering, we all share the universal foundations of maths and science and a similar outlook on life. The attitude of doing the best you can, going that bit beyond the specification, to make the best possible product, whatever it happens to be. Because you just never know when that little extra can make a big difference.<br />
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Quite often, when we do our jobs right, nothing happens. A Formula 1 car crashes backwards into a concrete wall at 150 mph and the driver walks away. The media call it luck, or maybe God's will. What they rarely mention is the truth: Thousands, possibly millions of hours of hard work by clever, educated, experienced engineers. To every single one of the architects, designers, testers and yes, even you bureaucrats who came up with and enforced the Tokyo building regulations, you have my utmost respect. So far as I am aware, nothing happened. No pictures flashed around the globe of skyscrapers that collapsed. No footage of thousands of sobbing bereaved Tokyo people. Other areas weren't so lucky, with fires breaking out and many people losing their lives. Let us hope that in future years that those areas can enjoy nothing happening too. It won't be luck that does that. It won't be God. It will be engineers. Invisible, un-named, unseen. Working hard to make sure nothing happens. That makes me proud.<br />
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Events move on however, and all the airtime is now being devoted to the Fukushima Daiichi nuclear plant. I'm not going to say much about nuclear plant engineering. At this time we don't have much information about how things failed and what the mechanims were, so it is difficult to say anything except to ask why they think it is a good idea to build nuclear plants near sea level on the coast facing the Pacific tectonic plate boundary, which has historically experienced powerful earthquakes and tsunamis. I believe nuclear power has a big future in the future low-carbon world, but not if they build fundamental weaknesses into power plants, relying on luck for nothing to happen.<br />
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Finally. I don't have many heroes on my list, and there are certainly no overpaid footballers or other sportsmen and women on it. The emergency workers who ran into the World Trade Centre towers when any normal human being would have been running away are certainly on it. Hell yes. I think that list has just acquired some more names; The engineers, technicians and others who are currently battling to stop Fukushima Daiichi nuclear plant becoming a hot Uranium dust emitter. These people must know that their lives are probably going to be severely shortened by what they are having to do. Ladies and gentlemen of Fukushima Daiichi plant number 1, you have my profound respect and admiration. Japanese popular culture has a long history of heroes and superheroes. I suspect they have just found some real superheroes, whose actions will be remembered long into the future.<br />
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I salute you all.Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-92137891081360689552011-02-04T13:37:00.000+00:002011-02-04T13:37:04.443+00:00Design Spark - Sort out your spam filters! & Electronics Engineering Heroes.I am posting this in reply to an item on RS's Design Spark site entitled <a href="http://www.designspark.com/content/electronics-engineering-heroes">"Electronics Engineering Heroes"</a>.Why am I posting it here? Well it seems to think I am a spammer and won't accept my submission. No appeal, no resubmission. Nada. Nice one RS. I invite anyone reading this to <a href="http://www.designspark.com/content/electronics-engineering-heroes">view the original articl</a>e, without which this post will mean very little!<br />
<br />
Steve Jobs was most certainly not the engineer, he was (and remains) a marketing genius. <a href="http://en.wikipedia.org/wiki/Steve_Wozniak">Steve Wozniak</a> was the engineer. <br />
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What does that say about engineering? That, subconsciously, even an engineer chooses a marketing man to symbolise engineering. Similarly, in the story of the transistor, William Shockley was largely a manager, and wasn't involved at the time the point contact transistor was created. The field effect transistor had previously been invented by several other people working independently, as long ago as the 1920s. I guess there was no marketing man handy to spread the word<br />
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If you want real electronic engineering heroes, try <a href="http://en.wikipedia.org/wiki/Robert_Watson-Watt">Robert Watson-Watt</a> the British RADAR pioneer - other RADARS were being developed, but it was Watson-Watt who managed to make the concept "fly", and without which we would have lost the Battle of Britain.<br />
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<br />
Equal with Watson-Watt was <a href="http://en.wikipedia.org/wiki/Tommy_flowers">Tommy Flowers</a>, the man who was able to make the WWII "<a href="http://en.wikipedia.org/wiki/Bombe">bombe</a>" decryptor, and went on to design <a href="http://en.wikipedia.org/wiki/Colossus_computer">Colossus</a>. The engineering was not in making it, but in getting it to run reliably, something which was considered impossible as it used nearly 2000 thermionic valves (tubes). The payout which the government gave him at the end of the war didn't even cover his personal investment in equipment.<br />
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Sadly, because both these men did their work during the war, a vast amount of it was an official secret and wasn't publically recognised until the 1980s.Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com1tag:blogger.com,1999:blog-3933619678696660447.post-27654801967559095732011-01-11T15:39:00.000+00:002011-01-11T15:39:19.356+00:006502 Factoid De JourToday's 6502 related fact - It seems that the 6502 was largely designed and taped out by ONE person, <a href="http://en.wikipedia.org/wiki/Bill_Mensch">Bill Mensch</a>. The one huge benefit of this was that the 6502 was right first time. This adds fuel to my hypothesis that the more people you have on a project, the more it is likely to fail. Similarly, the <a href="http://en.wikipedia.org/wiki/ARM_processor">ARM architecture</a> was designed by two people, one a hardware specialist (<a href="http://en.wikipedia.org/wiki/Steve_Furber">Steve Furber</a>) and one a software specialist (<a href="http://en.wikipedia.org/wiki/Sophie_Wilson">Sophie Wilson</a>), neither had much in the way of resources. The result was a processor that is in 90% of the world's mobile phones, and without which the iPhone just wouldn't be possible.<br />
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Keep your teams small!Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-15506291460891981472011-01-10T16:37:00.000+00:002011-01-10T16:37:09.946+00:00Reverse Engineering the 6502 - How they did itA few weeks ago I posted a link to www.visual6502.org which perfectly simulates the famouos 8-bit micro which was used in a huge range of computers. The same people have posted a series of lectures explaining how they did it, and what their future plans are. <br />
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<div class="separator" style="clear: both; text-align: center;"><iframe allowfullscreen='allowfullscreen' webkitallowfullscreen='webkitallowfullscreen' mozallowfullscreen='mozallowfullscreen' width='320' height='266' src='https://www.youtube.com/embed/HW9AWBFH1sA?feature=player_embedded' frameborder='0'></iframe></div><a href="http://www.youtube.com/watch?v=HW9AWBFH1sA"><br />
</a>Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-2927951804481613832010-12-05T04:09:00.000+00:002010-12-05T04:09:47.439+00:00Fluke 233 Multimeter Follow-up - WTF?The review of my Fluke 233 has proven surprisingly popular, comprising nearly half my blog traffic! I have had my Fluke 233 just over 4 months now, over which time it has had pretty light use. Which is why what I am about to say is a bit of a surprise.<br />
<br />
In <a href="http://electronicsdesigner.blogspot.com/2010/09/multimeter-review-fluke-233.html">my review</a> I wrote: <br />
<blockquote><strong>Batteries</strong>.<span> </span>400 hours estimated life is excellent. That probably works out at 3 to 4 years usage for me. But, when they go, it does mean potentially 5 batteries have to be replaced. </blockquote> I have used it for maybe 5 hours use at the outside, and not at all for the past month or so (sadly, my engineering has mostly been on paper or PC recently). That doesn't sound much, but it adds up to quite a few voltage and resistance measurements.Anyway, I came to use my Fluke 233 today and this met me:<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhluORYoSJTCLjo67j9eehgqUj1j5dJTSOQYtcRb9JDiaSTdF2uMrwaMeqcKEXWOTrVaW9I82h9lxaJw-pfdgIGf2CCGmZ7Z369HHkEXbVOSOherqeXvMI5dPEEKLjyYRrHwT0LOt7GlUFF/s1600/FlatBattery.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="273" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhluORYoSJTCLjo67j9eehgqUj1j5dJTSOQYtcRb9JDiaSTdF2uMrwaMeqcKEXWOTrVaW9I82h9lxaJw-pfdgIGf2CCGmZ7Z369HHkEXbVOSOherqeXvMI5dPEEKLjyYRrHwT0LOt7GlUFF/s320/FlatBattery.jpg" width="320" /></a></div><br />
Pretty much running on empty! Removing the remote head results in a BATT warning and no measurements are possible. If I am going to be installing a new set of 5 batteries every 4 months then it becomes a very expensive meter! I had thought that using high energy density AA cells was a good idea (the cells it came with were brand new Duracells with a very long use-by date), but maybe Fluke are covering up some nasty quiescent current use. I don't have my Fluke 77with me to test current at the moment, but swapping out the batteries allowed me to test the off-load voltages, which were all around 0.95-0.96 Volts.<br />
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Given the recently found RF vulnerability in the Fluke 87 V, it does make me wonder if Fluke are taking their eye off the ball. I will be investigating this further, because it surely cannot be right that a meter eats a set of 5 cells in 4 months, especially given such light usage. Watch this space!<br />
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In the meantime, if you have experienced any similar failures, please let me know!<br />
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Mike.Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-49038641377154329672010-11-17T02:56:00.000+00:002010-11-17T02:56:37.585+00:00Fake and Counterfeit ComponentsAs I have mentioned before, it seems to be increasingly common to experience IC supply problems, with long lead times becoming depressingly common. For example, I have three Analog Devices parts sat in my shopping cart with waiting times of 10, 11 and 15 weeks! This means that no matter how well meaning we are, it is massively tempting to look at the "grey" markets. Yeah, you know what that means. The risk of cheap, out of spec, and often totally unrelated components getting re-printed with the markings of much more expensive devices.<br />
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One example is the classic OPA627 op-amp much beloved of serious audiophiles around the world. This amp is expensive at the best of times, but last year the manufacturer and all the usual distributor stocks were empty. Conveniently, most op-amps have exactly the same pin-out and, unless you have the right test equipment, they are very difficult to tell apart. Search Ebay for them and see what a wide range of prices you get. Then consider that even in 1000+ quantity, TI prices them at $12:25.<br />
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Anyway, if you are contemplating sourcing from anything except the big distros, I would advise you read this article on counterfeit IC detection: <a href="http://www.aeri.com/detection-of-counterfeit.asp">http://www.aeri.com/detection-of-counterfeit.asp</a>Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0tag:blogger.com,1999:blog-3933619678696660447.post-91483773807891768482010-11-09T18:03:00.000+00:002010-11-09T18:03:35.368+00:00Making, Blagging, Ranting, Hacking.... and other stuff that ends in ing.I had a techy article in mind for this post, but I keep thinking of things to add to it, so it will have to wait a few days. Much of today's blog is inspired by the latest Amp Hour podcast ( <a href="http://www.theamphour.com/">available here</a> ). It is always good to hear other engineers from around the world talking trade, but never ceases to amaze me how universal the engineering culture is. The words may sometimes be different, but the underlying ideas and attitudes are almost always the same.<br />
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<span style="font-size: large;"><i><b>Making</b></i></span>. <br />
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I'm actually going to start with the British Broadcasting Corporation, good old 'Auntie'. Maybe it is just me getting older, but the main TV channels of BBC1, BBC2 and Radio 1 + Radio 2 seem to be increasingly unwatchable and unlistenable. Amazingly, I'm happy with that though. Radio 5, Radio 6, Radio 7, BBC 3 and BBC 4, despite being digital-only (except R5) are now consistently producing some excellent output. We have just had a short series on the origins of the UK's national grid electricity system, and last night I was listening to what used to be called "Pods and Blogs" but is now called "Outriders". Erm, WTF Radio 5?<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="http://www.bbc.co.uk/podcasts/series/pods" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="http://wwwimg.bbc.co.uk/podcasts/assets/artwork/266/pods.jpg" width="200" /></a></div><br />
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Accused of being London-centric (and it is, despite the inherently diverse nature of web content) they sent someone North (heavens no, they couldn't go themselves) to investigate Hackspaces and Maker groups around West Yorkshire, the home county of a certain Electronics Design Blogger (i.e. me).<br />
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They visited <a href="http://www.scrapstuff.co.uk/">Scrap Creative Reuse</a> down Kirkstall Road in Leeds. It is strange how people are seeing this as a totally new thing. When I was a kid in the 80s, childrens TV programmes were full of making-things-fromo-rubbish, and Arts and Crafts sales seemed to be on somewhere every weekend. It does feel a bit hippy circa 1973 though, and I'm not really sure how far the idea can go, beyond flogging stuff to the latest set of college Art students. Still, being in Art seems to pay better than engineering nowadays, so full respect to them. <br />
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Next, they visited <a href="http://leeds.hackspace.org.uk/">Leeds Hack Space</a> (at least I have heard of this one). I'm not sure how well they are doing, their web site doesn't seem to be updated much (not that I have room to talk there). This is a shame, because I think the idea of making resources publically available for a small fee is utterly briliant. Over on West Coast USA they have fully equipped engineering workshops available, stocked with high end professional equipment. With the decline of traditional industries here in Yorkshire, it is becoming the case that companies have to contract Mainland European / American / Chinese companies to do things that could previously have been done literally down the road. I think there is a sound commercial case to be made for a similar high-tech workshop with rentable facilities to be based around here. You can rent office space by the hour, even offices complete with networked PC facilities, I believe the same can be done not just for hardware, but for things like video production, digital photography, and even perhaps something like facilities for Ebay sellers. Local universities, colleges and schools are just not interested now, and in any case would probably hold a facility back from being used by business.<br />
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<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://www.oomlout.co.uk/" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://www.oomlout.co.uk/includes/templates/oomlout/images/logo.gif" /></a></div><br />
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<br />
<br />
<br />
They mentioned a local company I hadn't heard of before. <a href="http://www.oomlout.co.uk/">Oomlout </a>are a Halifax shop which sells Arduinos and related 'shields' (urgh, I still hate that word) plus all manner of related passives. they do seem to have quite a bit of content I have seen elsewhere, but I guess that's the nature of Open Source. <br />
<br />
If you are interested, he full podcast is available to <a href="http://downloads.bbc.co.uk/podcasts/fivelive/pods/pods_20101109-0330a.mp3">download here (11MB)</a>. Or <a href="http://www.bbc.co.uk/podcasts/series/pods">listen online here for 7 days</a>. The item on Hackspaces starts at 15 minutes. <br />
<br />
<span style="font-size: large;"><i><b>Blagging</b></i></span><br />
<br />
Anyway, back to The Amp Hour. Dave was commenting on how engineers shouldn't rely on free samples, and really shouldn't use them at all. I'm afraid we disagree there. As a self-employed design engineer, I am in a very "big loop". That is to say, in order to get any approvals with respect to design or (especially) budget, I have to phone someone, email them, and wait for them to pass an spproval up the chain, and down again, and eventually get some finance in place to buy stuff. I rarely have the luxury of total freedom to buy stuff as and when I want. As an aside, I totally agree with Dave and Chris here, how come we professional engineers aren't trusted with money? It probably costs £50 in man-hours to get approval for something that costs £10.<br />
<br />
Anyway, last week I ordered some samples from TI, they made it here from DigiKey 3800 miles away as the crow flies, 5800 as the plane flies, in 36 hours. I calculate that from the second I clicked submit, those parts <i>averaged </i>161 mph from Thief River Falls to Wakefield. Shame a couple of components are on back-order, but then they are back-ordered <i>everywhere</i>. In these days of strained budgets, 50 bucks worth of samples can make the difference between 'go' and 'forget it'. Thank you TI. I, for one, appreciate it.<br />
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Okay, loads more stuff to say, but I reckon I have waffled on long enough. Take care!Mikehttp://www.blogger.com/profile/02330775285331342432noreply@blogger.com0