On 1/24/2011 5:20 PM Jeffrey Angus spake thus:

On 1/24/2011 6:40 PM, William Sommerwerck wrote:

Set the audio gen to about 100kHz and connect the output across
the electro under test -- then connect the scope probes directly
to the same cap (not the generator). You should see a small
voltage at 100kHz on the scope.

If one takes that literally, the scope probes /will/ be connected
directly to the generator.

Did you leave something out?

Nope, it IS connected directly to the generator.
And the capacitor across both.

You see a reduced value of signal due to the ESR of the capacitor
vs the source impedance of the signal generator.

Pretty simple.

Not direct reading, but accurate comparison.

Skimming through a bunch of ESR meter schematics, this seems to be the
game plan for most of them:

Oscillator -- attenuator -- cap under test --
op amp/comparator -- rectifier -- meter

(osc. is usually around 50-100 kHz)

Gots to build me one someday ...


(the attenuator delivers only millivolts to the cap being tested,
avoiding electrolytic polarity issues and any semiconductor junction
resistances)


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.