Author Topic: How to use Ohms to test a capacitor?  (Read 13587 times)

slackmax

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How to use Ohms to test a capacitor?
« on: February 22, 2023, 07:13:44 AM »
I bought a multimeter to test a new capacitor, and tried to use Ohms to test it. I discharged it with a screwdriver, then I set the meter to 10K Ohms, and connected the red and black leads to the capacitor terminals (just 2 terminals on this cap).

The reading is supposed to go from zero and slowly climb upwards, if the cap is good, but the readout just said '1' and stayed there. 

I also tested a bad capacitor, which I just removed, and it also just says '1' on the readout.

By the way, I also tested the new cap using the microfarads scale, and it tested as good, at 10 microfarads. 

What am I doing wrong with the Ohms method ?

Tigerpine

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Re: How to use Ohms to test a capacitor?
« Reply #1 on: February 22, 2023, 07:38:51 AM »
It's been some years, but here's what I have.

Make sure you have the polarity correct with your leads, assuming the cap is polarized.
It's better to use an analog multimeter for this test (as opposed to a digital one).
You may want to increase the Ohm setting.

slackmax

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Re: How to use Ohms to test a capacitor?
« Reply #2 on: February 22, 2023, 07:47:24 AM »
It's been some years, but here's what I have.

Make sure you have the polarity correct with your leads, assuming the cap is polarized.
It's better to use an analog multimeter for this test (as opposed to a digital one).
You may want to increase the Ohm setting.

Thanks, Tigerpine. The cap has no markings on it near the terminals, so I assume it is not polarized. I tried it both ways, still got a '1'.   

I do have an analog meter. Will try that! thanks


bacchi

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Re: How to use Ohms to test a capacitor?
« Reply #4 on: February 22, 2023, 08:49:40 AM »
A cap only has measurable "resistance" when it's supplied with power. It's not a constant R, either.


bill1827

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Re: How to use Ohms to test a capacitor?
« Reply #6 on: February 22, 2023, 12:13:02 PM »
What's the value of the capacitor?

An ohmmeter will only give an indication of capacitance with large capacitors, if the capacitor is only a micro farad or two it will show as open circuit, which is presumably what your 1 is.

This method is only a very crude indication anyway and won't tell you anything about any other faults the capacitor may have.

I see it's 10 uF, the ohmmeter will tell you nothing about that capacitor.