How to test for electrolytic polarity?

[solarbot]

Hi,

I have a set of electrolytic caps which seem to have just the one polarity indicator and that is the leg length..... with the legs cut to the same length, is there a way to determine the polarity through testing?  Cheers.

[David Hess]

I have a set of electrolytic caps which seem to have just the one polarity indicator and that is the leg length..... with the legs cut to the same length, is there a way to determine the polarity through testing?  Cheers.

Leakage will be much higher in the reverse direction at low voltages, so a low value current source can be used to charge the capacitor in both directions and safely reveal the correct polarity.

[PA4TIM]

There are non polarized electrolytics.

[solarbot]

I didn't know that there were unpolarised electrolytic caps - this one has a long leg and a short leg so guessings its not one of them?..... although this one has NP on the casing and a diamond shape with dots at the corners so perhaps it is?

If I chargre the cap (rated 16V) with a 9V battery and then measure the voltage with a multimeter, I should see the volatge drop more quicky when reverse charged?

[bdunham7]

I didn't know that there were unpolarised electrolytic caps - this one has a long leg and a short leg so guessings its not one of them?..... although this one has NP on the casing and a diamond shape with dots at the corners so perhaps it is?

If I chargre the cap (rated 16V) with a 9V battery and then measure the voltage with a multimeter, I should see the volatge drop more quicky when reverse charged?

A photo would help identify them, although if they don't have any polarity indication and they say "NP" on them, that's a pretty strong indication that they are non-polarized.

[solarbot]

Thanks folks, I think learning that there are non polarised electrolytics and measuring the leakage gives me confidence that this is a non polorised capacitors - the body is also bigger than an equivalent polorised cap so it all makes sense.

Thank you, I have leanrt something new 

Cheers.