[sdiy] Trouble shooting cap's ESR values using 'acurate' table..

[Steve Lenham]

On 14/10/2016 15:39, Jean-Pierre Desrochers wrote:

> I recently bought this multipurpose LCD meter for caps ESR checks:
> http://www.ebay.com/itm/-/121518679234?roken=cUgayN&soutkn=3AH3Nl
>
> It's electrolytic caps ESR function seems to be quite precise
> even at that low price..
> Now I'm facing a problem. I need an acurate Cap ESR value table
> that has 'standard' values to check for when trouble shooting caps.

No such thing exists!

ESR depends on the construction and chemistry of the particular 
capacitor. For that reason, caps of the SAME VALUE will have very 
different ESR properties according to:

1. Manufacturer.
2. Rated voltage.
3. Case size.
3. Intended purpose (e.g. general purpose 10uF/25V caps will have much 
higher ESR than 10uF/25V caps from the same manufacturer that are 
intended for SMPSUs).
4. Age (ESR rises as electrolyte dries up).
5. Temperature when you take the measurement.
6. Probably other things I haven't though of.

ESR isn't even a tightly controlled parameter (let's face it, very 
little about electrolytic caps is tightly controlled - capacitance 
+80%/-20%, anyone?). Datasheets tend to specify a maximum value.

So you can either scour the datasheets for every individual electrolytic 
cap that you wish to test, looking for the original spec (assuming that 
you can even identify the manufacturer and product range), or just be 
pragmatic and set a maximum ESR value that your circuit can tolerate. 
The latter seems a better approach to me!

Cheers,

Steve L.
Benden Sound Technology