CAUTION CAPCITOR Nerd Food

I must plead some degree of ignorance to many of the finer points of ESR variation, nominal values, and its effect on different circuits. Take this with a grain or two of salt.

I wouldn't tend to suspect that input filter capacitors would be especially sensitive to small ESR changes. (The filter capacitors are among the more common ones to have trouble, partly because they often operate at higher temperatures.) Bad capacitors often have an ESR reading that is several times nominal, so checking and troubleshooting doesn't require the utmost of precision and detailed checking of specifications from data sheets.

As to a relation of expected ESR vs. capacitor specification, I think I saw that once in a data sheet, at least for that specific class of capacitor. What the general relation was I don't remember.

Drew,

Señor, the caps after the full wave bridge rectifier in a switched power supply (MeanWell Megawatt) are the ones most sensitive to ESR variance? Dammit, old age forced me to forget the handle of the converter expert on this forum. I'd sure like his input as well! (that's an exclamation point).

PANASONIC offers some excellent 10,000 hour low ESR caps (not inexpensive). Lessening of capacitor life in relation to temperature is not linear. Is there a general rule or curve that can be used with regard to higher voltage electrolytic's?

Gene&Ginny wrote:
ESR Tester Instructions:
Firstly Short connected two test leads, then boot to complete the boot automatically zero.
The road (non-road) the results of the measurement data Standard capacitor ESR (equivalent series resistance) value comparison (See Forms).

:h

Translation: Short the test leads together (with no capacitor to test in place) and hit the reset button. The purpose of this is to let it figure out the resistance of the test leads themselves. It's kind of like the tare function on a kitchen scale, when you wish to weigh the garlic and not the bowl it's in.

Once zeroed out, hook it up to the capacitor and read the ESR and check it against specs or, lacking anything more specific, the table printed on the front of the unit.

If you're wondering about ESR, it's basically a measure of how far the capacitor varies from an ideal capacitor, using a model of an ideal capacitor in series with a resistance. Electrolytic capacitors in particular when they age often show an increase in the ESR but not so much a decrease in capacity. This can cause all sorts of circuit problems.

If you think the description of that one was hard to understand, check out this one, as shown with this illuminating snippet:

Main purpose:

1, An accurate measurement of capacity greater than 0.1uF capacitor ESR. CBB can be measured capacitance ESR. Resolution of 0.01 Euro.

2, measuring 0.1uF to 10uF capacitor capacity, the capacity of the smaller higher accuracy. Resolved to 1nF.

3, the accurate measurement of 0 to 1200uH inductor. Resolved to 0.02uH.

4, measuring less than 20 euro no sense of resistance, accuracy of better than three and a half meter, distinguished to 0.01 Euro.

The four purposes, fall within this table of the main span, measuring effective and high precision.

ESR Tester Instructions:
Firstly Short connected two test leads, then boot to complete the boot automatically zero.
The road (non-road) the results of the measurement data Standard capacitor ESR (equivalent series resistance) value comparison (See Forms).

:h