Jeff Liebermann wrote:
Phil Allison


** You went to lot of trouble to see the obvious.

Cap-B was one that had failed with high ESR. There was plenty of data
and anecdotal evidence on how a normal capacitor would act. I wanted
to see how a defective capacitor acted.


** Well, that depends how *defective* it actually is !!!

An electro that has lost nearly all of its fluid and reads off-scale on Bob Parker's meter is not likely to come good with a bit of heat.


I also wanted to see how the
ESR meter functioned with small value and size (0.22uF 50v) caps,
which was Cap-D. The change in ESR with temp was far less radical
than the others.

** Even a 0.22uF film cap reads 7 ohms on the Bob parker meter - IOW the impedance of the thing at 100kHz. Bob's meter does not read actual ESR values, rather it reads impedance vales at 100kHz.

This *fact* is pointed out in the instructions and the lowest value electro you can reliably test is about 1uF - as shown on the front panel table.

A man has gotta know the limitations of his ESR meter.
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All I did was try a few 450V electros, heat them with a hot air
gun until they were darn uncomfortable to hold and note that in
every case the ESR reading had plumeted by 5 to 10 times.

I wasn't interested in high voltage electrolytics.


** They have higher ESR values than low voltage caps, so there is plenty of room for ESR readings to come down without approaching the low reading limit of Bob's meter.

I used a value of 47uF, so its reactance at 100kHz was negligible.

Pays to think ahead, you know.


..... Phil