Some surprising conversations happened during the first week of the semester.

HAMEG Instruments HM404-2 40MHz Analog Oscilloscope

Oscilloscope: Wolverine in Disguise

Why Don’t You Just…?


In AC Circuits, I gave the students a list of all the controls on their scope.  Mission: find out what they do.  They got them all except for the difference between AC and DC coupling (notoriously difficult for beginners to understand).  By the end of the class, not only had most people applied the idea to a measurement, but several students proposed alternate ways to do it: “Couldn’t you just adjust the volts/div?”  “Couldn’t you just adjust the vertical position?”  Understand, too, that this was not coming from the advanced students who’ve had a scope in their basement for years — it was the students who until last week were treating their oscilloscope like an angry, injured wolverine.  The following day, a student was demonstrating some oscilloscope skills with lots of confidence.  I asked if she still saw the scope as a rabid animal.  “No,” she replied, “it’s a fluffy little bunny.  It’s only occasionally badly-behaved.”

They talked to each other.  They strategized.  They struggled.  They noticed effects they’d never noticed before and gave them names (AC coupling is now called “the bounce effect”).  In the following lab, the students invented the three diode approximations.  I was just about to open up some questions about how to analyze diode circuits when a student cut me off to say “why don’t you just” use the knee voltage?  And lo, the 2nd diode approximation was born again, for the first time.

Theory: the skills list seemed to help them cut loose and experiment.  They spent all afternoon turning knobs just to find out what would happen.


Three students turned in homework (not required) — sometimes the same homework over and over.  In each case, it helped me figure out what misconception was holding them back.

One of them redid his practice problem and showed me his new answer, which was correct.  He asked if he had to pass it in.  I said no.  His answer: “Good, I have to go check my skills list and see what this proves.”  My goodness, thinking about the meaning of practice problems?


Some students are working through the lab book during shop time.  They keep a constant eye on the skills list to figure out what’s important.  They could do this just as easily by reading the purpose — that thing printed in bold on the first page of the lab.  Reality: they don’t read the “lab purpose.”  They do read the skills list.  Someday I’ll have a clear theory about why.

Most students are not working through the lab book.  They’re picking out one skill at a time and trying to find a shorter, easier way to prove that they can do it.  In the process, they are designing experiments.  Sometimes they get to the end and realize that so many variables changed, they can’t demonstrate any one thing.  They go back and do it again, with controlled variables.  Seriously.  Several times it has ended up being the same circuit as in the lab book.  On two occasions it resulted in burnt resistors.  Good conversations resulted.

They’re even tackling “quiz-type” skills in the shop.  I give them no guidance on this.  The upshot: they create test questions for themselves, either on paper or by finding ways to translate paper skills into hands-on circuit skills.  Again, nothing was stopping them from doing that before.  In fact, last semester, bribed and bartered and begged them to do just that.  This semester I haven’t even had a chance to bring it up.

Time Management

On Friday, a student asked for the next topic skills list.  That’s never happened to me before.  He proposed to integrate this unit’s skills with the next unit in order to get a 5.  I accepted.

Gaming the System

The “game layer of education” mostly makes me feel like someone’s dragging my teeth across a chalkboard.  But this is something I should have learned from casual gaming years ago:  make the first few tasks very short.  It sucks people in.  Note to self: find 1-2 short, simple skills that most students can complete without any help.  List them first on the skills sheet.


Our first quiz was this week.  We reviewed it right away.  Several students were surprised to find out that this “counts.”  They asked me when the “real test” was.  I asked them what they thought was a better basis for their grades than their skills?