Is there any reason why the method of using a function generator and scope, as described here: http://geoffg.net/Measuring_ESR.html could not be used at a higher frequency (say, 100KHz) to find the ESR of smaller value caps? (He is using a 1KHz wave and can only measure down to 10uF). Also, I note that he is using a 10v signal while the ESR meter designs all seem to generate a fraction of that (IIRC, Bob Parker blue ESR meter is 100mv output) so as not to turn on any semi-conductors in the circuit. Any reason not to turn down the output voltage to something similar?
I answered my own questions: it all works just fine. Larger caps show a virtually flat line with a very narrow spike at the start of each square wave input. A 0.47uf cap has a slight ripple waveform (with the aforementioned spikes). A 0.1uf cap produces a shallow triangle wave between the spikes. A 3pf cap passes the square wave virtually unchanged. Seems to work equally well in circuit as without.
So, I now have built an ESR with a component count of 6: 2 bnc connectors, 1 project box, 1 51 ohm resistor, 1 scope and 1 function generator