[sdiy] Are power electrolytics microphonic?

harry harrybissell at prodigy.net
Thu Apr 5 06:16:48 CEST 2001

Charge them up... scope them on AC and tap them... look for the frequency

of any ringing from the mechanical excitement...

Then run them above 105C... they'll die soon

H^) harry (who is also working on a cap decision... Big electrolytics or
film caps...?.)

Toby Paddock wrote:

> Semi-OT:
> I'm doing vibration testing on some fairly large (but not real large)
> electrolytic caps. And I was wondering if I could find the resonant
> frequency of the guts by charging it up thru a high resistance and
> looking for an AC signal when the stuff starts flexing inside.
> (That sentence was way too long.)
> Seems like if the layers flex and move, it might change the
> capacitance. So with a constant charge, that would vary
> the voltage.
> They are like 450 WVDC and I don't know the C value. The
> aluminum can is about 1.25 inch dia. by 3.5 inches long.
> Ideas? Opinions? Advice? Point and laugh?
> Thanks,
>  - -- -  Toby Paddock

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