With the transformer box complete, I was able to finish Lab 2. The last exercise required one to combine a 10kHz signal from a signal generator with the 60Hz output of the transformer, and then use filters to isolate one or the other.
Once again, this was an exercise in understanding impedance. The lab mentions that the signal generator has a 50R output impedance. Great, I thought! I know they suggest that input impedance of the next stage (filter) should be 10x time the output impedance of the previous stage, so I’ll set the resistor (impedance of an RC filter is just the resistance of the R component) to 500R!
Except, of course, that there was also a 1k resistor in-line with the signal generator (to limit current). So my output impedance was actually 1050R.
Additionally, I set my cutoff frequency poorly in earlier attempts. Trying to separate 60Hz from 10kHz, I set the f3db frequency of the filter at 1kHz. This didn’t provide nearly enough attenuation.
After some help from the awesome folks at the eevblog forum, I made it work. An R value of 10k solved the impedance issues, and cutoff frequencies of about 5.3kHz (C=3nF) for the high-pass and 636Hz (c=25nF) for the low-pass got the signals relatively clean.