I might try duplicating an impedance bridge with a pair of 10 turn
potentiometers and a couple of range switches. The ESI 250DA and a
couple of others from that era used eye tubes as null indicators which
an oscilloscope display could easily handle. I suspect taking
advantage of a 2 dimensions would make it possible to visualize
dielectric absorption or other imperfections.
Getting from the reactance and D/Q settings to the oscilloscope
readout would be tricky though. There I would go the full
microcontroller route to generate the necessary readout control
signals which would also allow easy conversion between D, Q, and ESR.
On Mon, 21 May 2012 08:11:09 -0000, "fred" <fredschneider@...>
wrote:
The best way is to look at phase that is what they do in a IV impedance meter, a high end LCR meter or a VNA. And because this is the only good way you do not see agilent or Fluke ESR meters. If you build it right it would be foolish not to make an LCR meter out of it because it would be allmost as complicated. If you have capaitance and D ( old LCR bridged let you measure that) and calculate Xc from that on the working frequency ( ESR changes with frequency but not so much a bad cap looks good on low frequency, for instance 5 mOhm at 100KHz can be 100 mOhm at 100 MHz. That is 20x higher but also very high in frequency. It only becomes higher so if the cap is bad it will be also at 100KHz or lower.
David Hess