Found in a 1992 book, this circuit is intended for operation with audio signals. Equivalent operational amplifiers can be used. The optical coupler is an unusual type today.
This circuit is from 1968 General Electric documentation. It can certainly be adapted for any...
This tester from a 1960 magazine is only for capacitors with insulation voltages above 200 V (110...
Found in a 1991 publication this circuit can be assembled with more modern components. We can use...