On 5/17/07, Russell McMahon <apptech@paradise.net.nz> wrote:
> > Can one easily measure the ESR of a capacitor configuration?
>
> Yes.

Russel, then you know why that methode (and usually any cheap and dirty
methodes you may found on the internet) is not good ?

>
> There are cheap enough meters to do this for you but you can do it
> with an oscilloscope, a square wave source and a resistor if you wish.
>
> Here's an example
>
>        http://octopus.freeyellow.com/99.html
>
> What it does is to rely on the fact that the voltage across a
> capacitor cannot change instantaneously. If you apply a square wave
> voltage through a resistor the initial step in voltage at the
> capacitor will be caused by voltage divider action between the input
> resistor and the ESR. After the leading edge occurs the capacitor will
> start to charge/discharge and you will get a subsequent exponential
> waveform but the initial step allows you to measure the ESR.
>
> Example:        Imagine you have a 10 ohm resistance square wave
> source with a 1 volt peak-peak square wave and a 0.33 ohm ESR.
> At the square wave edge the 10 ohms and 0.33 ohms will form a voltage
> divider so you can expect to see the capacitor voltage step by 1V x
> (0.33)/(0.33+10) = 32 mV.
>
> See above article for several practical circuits and a more detailed
> explanation.
>
>
>
>
>        Russell
>
>
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