Capacitor ESR reading

[markusjames]

Hello!
Need some advise please. I have 1000uf 50v capacitors that has readings of 1940uf using ESR meter with 0.1 ohms and others 0 ohms. I know that capcaitors should not be less or more than 10-20% tolerance. Are all my caps with these readings considered shorted or bad? Thank you!

Cheers,
Markus

 

[Nigel Goodwin]

I know that capacitors should not be less or more than 10-20% tolerance.

You 'know' wrongly - electrolytics capacitors usually have massive tolerances, 10-20% would be pretty rare - something like -20%/+50% would be more common.

Measuring the capacitance of a large electrolytic isn't easy, and likely to be pretty inaccurate anyway, as leakage will make it appear larger than it actually is, particularly with such low power testing, as with an ESR meter or capacitance meter.

What sort of ESR meter are you using?, the ESR of 1000uF should only be a fraction of an ohm - if you want to see if they are short or not, simply put your multimeter across them on the ohms range. However, if it's giving you a capacitance reading, then it can't short.

 

[markusjames]

Hi Nigel! Thank you for the correction. Can you say that my 1000uf reading of 1940uf is bad?

 

[Nigel Goodwin]

Hi Nigel! Thank you for the correction. Can you say that my 1000uf reading of 1940uf is bad?

No, it's almost certainly NOT bad - you don't get faulty components reading high - just like a car, you don't take your back to the garage complaining it does 300mph, it just can't happen.

If you want a more accurate reading (but why?) then you would need to test them under more practical use to take account of leakage.

 

[markusjames]

Thank you for the info

 

[Grossel]

I guess you're trying to measure the capacitor while still on PCB, and so there are probably another one in parallel.

 

[markusjames]

You are right! That's why I have higher readings. Thank you!