Gas station without pumps

2017 April 11

Maybe eliminate bench equipment next year

Filed under: Circuits course — gasstationwithoutpumps @ 22:40
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One of the BELS (Baskin Engineering Lab Support) staff had an interesting proposal for next year: maybe, instead of tying up a lab with $200,000 worth of bench equipment next year, the applied electronics course could have students rent a box containing an Analog Discovery 2 (with USB cable and power supply).  Each box would cost about $200, and students could rent them for about $30 a quarter (there is precedent for this approach—it is used in the first programming course for Computer Engineering).  As long as the failure rate for the USB oscilloscopes is low enough, the rental would cover replacement about every three years.  Furthermore, students could purchase the boxes at the end of the course for cost minus the rental rate.  Given the attractiveness of the instrument to bioelectronics students and to hobbyists, I suspect that about 1/3 of the boxes would get bought each year.

The initial investment is relatively modest (about $20,000 for 100 boxes) and the change would make it much easier to schedule the labs next year—all that is needed is a room with enough electrical outlets and enough tables and chairs (not even fancy lab benches).  We’d also need to have soldering irons and fume extractors, but those have already been purchased (though we may need to get more, as they keep getting used for other courses and other needs.

I’m now trying to decide between two options:

  • Stick with the conventional bench equipment we have.
  • Switch to using the Analog Discovery 2 exclusively (with maybe a handheld DMM for use as an ohmmeter)

The conventional bench equipment approach has the advantage of teaching the students how to use equipment that they are likely to see again in other courses or in research labs. The Analog Discovery 2 is not suitable for high-frequency work, so students going into work that need higher bandwidth will have to learn conventional bench equipment—the current course is the best training available to the students and helps them considerably in the EE lab courses, where they are expected to figure out the rather complicated bench equipment on their own. The bench equipment approach also requires no extra expenses for the students.

The Analog Discovery 2 approach has the advantage of allowing the students to do almost all the labs anywhere.  With the lab time for 5 sections coming to 16 hours a week, not having to share a lab with another course would be a welcome relief, both for us and for them.  (Also, we wouldn’t have to deal with all the damage that the untrained, unsupervised students in the first EE class do to the equipment.)  The Analog Discovery 2 provides an easier-to-use interface for all the equipment than the rather clunky old interfaces of the bench equipment in the lab—some of the labs that now take hours could be done in a few minutes, because of the better integration of the instrumentation. Furthermore, the students would be able to buy at very low cost a piece of equipment that would serve them very well in other courses and as hobbyists.

If we did go with the Analog Discovery 2, I would have to rewrite big chunks of the book to adapt the labs and remove (or separate to different sections) references to the bench equipment. I’m already planning to do a fairly major overhaul of the book this summer and fall, so that’s not a major argument one way or the other.

Faithful readers, advise me! Should I stick with the bench equipment or should I move to BELS renting out Analog Discovery 2 boxes next year?  What other factors should I consider in making the decision?


  1. The advantages of renting digital scopes and being able to use them at any time appear to greatly outweigh the advantages of becoming familiar with standard bench equipment. Limited access to equipment was quite frustrating for me when I was in undergrad labs.

    Comment by miguelaznar — 2017 April 11 @ 22:56 | Reply

    • Limited access to the lab is indeed one of the driving factors in leading me to think about using the USB scopes.

      When the only USB scopes on the market were rather low-quality in both hardware and software (like the Bitscope one that I used for a few years), I couldn’t justify having students use them instead of a “real” scope, but the Analog Discovery 2 is a powerful enough instrument that it really can replace the bench of equipment for this level course.

      Students still need supervised lab time to learn to use the tools and debug circuits—only about 10–20% of the students I see have enough confidence and ability to learn debugging on their own, but the lab need not be equipped with expensive bench tools any more.

      Comment by gasstationwithoutpumps — 2017 April 12 @ 08:41 | Reply

  2. I really like the idea of the students being able to have equipment they can use to anywhere — especially back in their rooms. This seems like a slam dunk. And you could have an orientation to some of the standard higher frequency stuff as part of the curriculum …

    Comment by alanone1 — 2017 April 12 @ 03:33 | Reply

    • Learning to use the oscilloscopes, multimeters, and function generators is more complex than a short orientation can provide. Even after 35 hours in the lab last quarter, a number of students are still uncomfortable using the function generators and oscilloscopes in the lab. Part of the purpose of the course is teaching students to use electronics tools, but there is some question in my mind whether it is better to teach the old clunky interfaces of the bench tools or to teach the easier-to-use interfaces of the Analog Discovery 2. Perhaps for a first course, the simpler but more powerful modern interface is better pedagogically, but then I fear that they may never learn how to use the more common older interfaces.

      I can’t count on students getting the lab skills in later courses, because EE does a terrible job of teaching lab skills, here, perhaps because most of the faculty never spend time in the undergrad labs. One EE faculty member does a good job (he taught me how to use several of the pieces of equipment), but I can’t count on students getting him for a lab course (and he is likely to retire about the same time I do).

      Comment by gasstationwithoutpumps — 2017 April 12 @ 08:36 | Reply

      • In the 50s (high school for me) we used to solve this problem by building Heathkits — they had pretty good VOMs, a very workable oscilloscope, etc. And there was a lot of practical “feel” gained by building your own test equipment ….

        Comment by alanone1 — 2017 April 12 @ 08:42 | Reply

        • I built a Heathkit VTVM (vacuum-tube voltmeter) and oscilloscope (in the 60s, rather than the 50s), and learned a fair amount from doing it, but the effort is much larger than we have time for in this course. Also, the quality of the what you can build yourself is much lower than what you can buy cheaper, as is the case for so much electronics these days.

          The PteroDAQ data acquisition system I’ve been using is a good example of a do-it-yourself system (my son wrote most of it, and I’ve added to it). It is very cheap (about $15 for the hardware, with free software), but it is much less featureful than the $200 Analog Discovery 2. Digilent is working on an open-source USB oscilloscope that would appeal to hobbyists, but it will run about $100 and be much less than half the value of the Analog Discovery 2 (though still an order of magnitude more useful than the old Heathkit oscilloscopes).

          One decision I’ll need to face if we use the Analog Discovery 2 is whether to phase out the use of PteroDAQ. I hate to abandon the project, since it provides such a cheap entry point to looking at (low-speed) electronics waveforms, but it would be hard to justify if the students have access to the Analog Discovery 2. I wonder if I’ll need to write the book to have 3 sets of lab instructions/exercises (one for Analog Discovery 2, one for conventional bench instruments, one for PteroDAQ).

          Comment by gasstationwithoutpumps — 2017 April 12 @ 08:53 | Reply

  3. These days we give students a lab kit for their first year circuits labs. Seems to work for us.

    Comment by plam — 2017 April 12 @ 07:13 | Reply

  4. What they said.

    Comment by gflint — 2017 April 12 @ 07:29 | Reply

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