[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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