"Arfa Daily" wrote in
:


"Leonard Caillouet" wrote in message
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wrote in message
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I have a question about ESR measurements.

I have been doing some reading about ESR and the literature
indicates it can be a strong function of frequency. In the design a
SMPS I assume the ESR of importance is at switching frequencies
(at least for the line side capacitor).

I have also noticed that often the measurement made in trouble
shooting are low frequency measurements (step function - looking at
the abrupt change in voltage).

Is the above accurate and if so when a cap goes bad do the low
frequency measurements catch the majority of the high frequency ESR
failures. Are there significant failure modes where a low frequency
ESR measurement would miss the higher frequency ESR failure?


Thanks Much,

Most of the ESR meters that I have seen test in the 50-200 kHz range.
This pretty much covers the switching frequencies of most power
supplies, at least in consumer equipment that I am familiar with.

Leonard


Exactly ditto.My Bob Parker meter works at around 100kHz, and I have
never had a problem with it picking up any (several per week) faulty
caps.

Arfa




one thing to consider is the waveform of the usual switcher;the cap has to
deal with a fast rise waveform rich in harmonics.2nd and 3rd harmonics will
still have a lot of energy.

your usual 60hz XFMR supplies dealt with a sinewave.


--
Jim Yanik
jyanik
at
kua.net