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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