Over the decades I have doodled with a circuit design to make a handy battery powered pocket tester. The premise was to make a free running oscillator, where the frequency of the oscillator would vary based on termination impedance.
Ideally it would provide recognizable frequency discrimination between 0-2-4-8 ohms, all the way up to 600 ohm-2k-10k-higher. Obviously a nonlinear scale.
The oscillator would make enough output to actually be audible (while not very loud) when connected to a speaker, while not so loud, that it would cream a mic input.
I planned to use a square wave, or some variant waveform, so even a LF pitch, could have MF and HF output to exercise all loudspeaker drivers.
So kind of a swiss-army continuity tester, impedance checker, yadda yadda...
Another one of my projects I never finished. FWIW this would have to sell for next to nothing, so not much dollar sales volume to speak of and encourage me to finish.
JR
