LTI Lissajous explanation document

[Ted Pavlic]

I teach an introductory course on basic electronics and
instrumentation. I recently put together a document on using Lissajous
figures to experimentally determine the phase shift of an LTI system.
I thought someone here might find it useful:

http://www.tedpavlic.com/teaching/osu/ece209/lab1_intro/lab1_intro_lissajous.pdf

It's a short document (2 pages). I included a couple of graphics that
I think could be helpful.

*) The graphic on the first page shows how to use the shape and
rotation direction of the Lissajous figure to properly place the phase
shift (i.e., determine which quadrant the angle is in).

*) The graphic on the second page gives a simple laboratory procedure
for determining phase shift (including steps that put the phase shift
in the correct quadrant).

 

[Ted Pavlic]

That's an accurate statement (in my experience). The last time I saw a

lissajous image was when I was a kid (30+ years ago). I tore apart an old tv
and hooked my stereo's amplifier outputs to the horizontal and vertical
deflection coils. I used to watch that thing for hours.

I appreciate that, and so do the students, but the laboratory
experience (which is out of my hands) is pedagogical. It's not
entirely about training in modern methods. For sophomores in college,
there's plenty of value in this exercise (which is prefixed by plenty
of "In the old days, before engineers knew how to add, . . ." so that
I don't feel disingenuous). The equipment is there as a vehicle for
education; the training is just bonus, and there will be plenty of
modern training.

I haven't seen many good references on Lissajous figures for this
application, and those that I've found are either inaccessible to
sophomores or lack too few details to be useful. I'm trying to fill
that gap a little with that document, and I thought a few people might
be interested.