"John Larkin" wrote in message
...
On Fri, 06 Jul 2007 02:54:06 GMT, "Lord Garth"
wrote:


"John Larkin" wrote in
message
.. .


It doesn't measure ESR, it measures a sort of twisted/nonlinear/offset
version of total impedance. It probably will tell open electrolytic
caps from good ones, but the thing the needle indicates isn't ESR. For
very big C's with low ESL (ie, when Z is mostly ESR, and low ESR at
that) then it mostly measures ESR.

For a similar level of complexity, one could measure true ESR. Or for
a lot less complexity, one could measure what this thing measures.

John


Circuit please...


Something roughly like this, maybe. This is a 2-minute hack, so don't
jump all over it right away; a real design would take more time.
Basically, it's an oscillator that dumps current into the cap, and a
synchronous detector to remove most of the orthogonal component. It
ain't perfect, but should be a lot better than a scalar measurement.

John



Thank You...