[ARC5] Aging Electrolytics
Kenneth G. Gordon
kgordon2006 at frontier.com
Fri Jan 30 23:18:25 EST 2015
On 30 Jan 2015 at 18:33, Richard Knoppow wrote:
> ESR may not always be the right criterion.
Correct, but I use it in conjunction with a full-voltage leakage tester.
My ESR meter has a list of maximum ESR per electrolytic capacitance. If any
I have exceed that, out they go.
> Rather leakage, or
> parallel resistance may be the right thing to look for. Electrolytics
> have fairly high ESR even when new.
Well, at least when compared with mica or even paper, and far more than
most of the new caps.
> Of course the lower the better, but
> leakage is often critical. Its possible for a capacitor of any type to
> measure low ESR but still be leaky. ESR is measured using AC, it is the
> equivalent of Q for a capacitor, leakage is measured with DC, an ideal
> capacitor should not pass DC at all, practical ones have some equivalent
> parallel resistance because nothing is a perfect insulator, but it
> should be low enough not to cause problems to the circuit the cap is
> used in.
My "Condenser Checker" applies switchable voltages up to a full 450 VDC to
the caps. Leakage is very easily discernible.
> Leakage may not show up with low voltages so its usually
> recommended that , at least for electrolytic caps, it be measured at
> something approaching operating or rated voltage. I have found for
> paper caps an ohm meter capable of reading high values of resistance,
> for instance a Hewlett-Packard 410B or C or an -hp- 412, will usually
> indicate when leakage is excessive. For some caps something like a
> "megger" is better. Both high ESR and leakage are bad.
Yup.
Ken W7EKB
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