Capacitor esr meter 2012-01-27

Menticol submitted a new article:

Capacitor ESR Meter - What is ESR and How Can It be Tested?

As the allmighty Samuel M. Goldwasser says, "ESR (

What is ESR and How Can It be Tested?

As the allmighty Samuel M. Goldwasser says, "ESR (Equivalent Series Resistance) is an important parameter of any capacitor. It represents the effective resistance resulting from the combination of wiring, internal connections, plates, and electrolyte (in an electrolytic capacitor). The ESR affects the performance of tuned circuits (high ESR reduces the Q factor) and may result in totally incorrect or unstable operation of devices like switchmode...

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Great info Menticol. Thanks for sharing

i've been repairing all types of electronics for over 40 years, and ESR meters are definitely a must-have, especially now that the market is flooded with marginal capacitors (when new) from the far east. electrolytics have always been a high failure item, but in recent years, a lot of caps are made with marginal to poor electrolyte formulations, and barely make it past the warranty period of the equipment they're in. plus the fact that power supplies never really shut off, they just go into sleep mode, dries out caps even more.

can capacitor is used to deliver power?

Hi there,


The thing about ESR in capacitors is that when we use a cap in a circuit the ESR becomes part of the circuit too, and thus part of the feedback system in general and sometimes has to be carefully accounted for. The interesting thing is that in some regulators at least some ESR is actually a good thing, as it actually helps the feedback system stability. A perfect capacitor can sometimes be a problem in these kinds of circuits.

One way of testing the ESR is with a scope and a square wave generator and a series resistor. Looking at the current and voltage reveals the ESR that would be in effect in a switching circuit.

Funny story...
I called an electronic store near here about 10 years ago and asked if they had any "Low ESR capacitors", and they asked in response, "What is a low ESR capacitor?". I couldnt believe that they didnt know what this was.

Here is a link to one I built, works great. Equivalent Series Resistance Meter