How Do I Measure and Test Capacitors with My DMM

[Ncuab]

How do I measure and test capacitors with my DMM?  Here's a picture of it:



Thanks everyone!

[Ciaran Haslett]

Short answer is you can't.  It doesn't have a capacitance function.

Long answer is you can still test if a capacitor is functioning by using the resistance function.  An open cap will display an open circuit, a shorted cap will display 0V and a functioning cap will ramp up resistance.

You could also build a small test circuit with a 555 timer and some math but that seems fiddly for a job you are going to do over and over.  I'd suggest getting a better metre that tests everything we use...resistance, caps, transistors, diodes etc.

Actually I just seen yours does test diodes and transistors.  So maybe look around for a cheap capacitance tester to complete the set.

I eventually bought this and this.  These will measure semicondutors and passives automatically in about 5 seconds.

They are expensive and probably too much for me as a hobby builder but the sheer convenience and accuracy they offer gives me confidence that most of my builds now fire up first time.

EDIT:  I meant 0 Ohms

[knight_yyz]

You need a DMM with symbol #13 to do caps

http://media.fluke.com/images/dmm-dial-card-715x360.jpg

[Luke51411]

There are some Chinese testers that do a few other useful things on ebay for around $15-$20 that are pretty useful. something like this http://www.ebay.com/itm/Mega328-Transistor-Tester-Diode-Triode-Capacitance-ESR-Meter-MOS-PNP-NPN-LCR-/141643111145?pt=LH_DefaultDomain_0&hash=item20fa965ae9

[motterpaul]

Yeah.... but to answer the original question, do this. Take your cap out of the circuit. Connect the red & black meter probes to the opposite cap leads (+ and -), it's most logical to go red to + if the cap is polarized.

Turn the meter to measure a higher ohm resistance - like 200k. Then disconnect the + probe, turn the meter to the 2k Resistance setting and reconnect the red probe.

If the cap is good you should see that it picked up a bit of voltage from the meter the first time, then when you reconnect a good cap will usually measure that it still has about 600 ohms in resistance. You will see that number slowly fall as the cap drains.

All this tells you is whether or not the cap still seems to be good or bad (that it can hold some voltage). If you get 00:00 when you reconnect (no resistance) you have a bad cap.