So I got a bunch of surplus components, there are a lot of soviet semiconductors, resistors, caps etc. Ccan anyone point me in the right direction of testing if the caps are good, for large ones I use my multimeter's ohmmeter and see if they charge, but the smaller values don't even create a flicker. Is there any way to test these?
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\$\begingroup\$ For example by measuring the frequency of an RC oscillator. \$\endgroup\$– vennyCommented Sep 15, 2014 at 7:16
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\$\begingroup\$ Thats actually a great idea, so I would basically create an audio oscillator circuit and when it won't sound, the cap is busted, right? \$\endgroup\$– LimiterCommented Sep 15, 2014 at 7:26
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\$\begingroup\$ That depends on what you call small value. With a few picofarads, it is not possible to make audible oscillations, without using a mixer (i.e. like in a theremin). \$\endgroup\$– vennyCommented Sep 15, 2014 at 7:39
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\$\begingroup\$ Values all over the spectrum, I want to sort em out and discard any bad ones. \$\endgroup\$– LimiterCommented Sep 15, 2014 at 8:02
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I would recommend picking up a cheap capacitance meter or LCR meter.
http://www.ebay.com/sch/i.html?_nkw=capacitance+meter
http://www.ebay.com/sch/i.html?_nkw=lcr+meter
There are several available on ebay for about $20. Not only will you know that the cap is good, it will tell you the exact value.
answered Sep 15, 2014 at 7:30
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\$\begingroup\$ Thanks, I didn't know these existed, I am just a beginner :) accpting answer and will get one. Possibly get a DMM too, the one I am using is a cheap analog MM. \$\endgroup\$– LimiterCommented Sep 15, 2014 at 7:41
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\$\begingroup\$ As per my reading, the question is about testing the capacitors quality; and not their value. So I think to test the quality of capacitor, you must measure the ESR value. For that you must have an ESR meter. Search on google or ebay or any website to find about ESR meters and how to buy them. \$\endgroup\$– DamonCommented Sep 15, 2014 at 7:43
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\$\begingroup\$ ESR is really only a good measurement for large caps (e.g. electrolytic). For small ones, it's usually so small that it's a real pain to measure. \$\endgroup\$ Commented Sep 15, 2014 at 7:46
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\$\begingroup\$ Thanks for more information. But then could you please tell me procedure to test quality of capacitors with LCR meter. \$\endgroup\$– DamonCommented Sep 15, 2014 at 7:49
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1\$\begingroup\$ Depends on what you are looking for. Generally if the capacitance is within tolerance, it's fine. Electrolytic caps are the only ones you really need to worry about because they can degrate over time due to their construction. This is where the ESR measurement can be handy. Good (expensive!) LCR meters will either tell you the ESR directly or they will give you the D or Q factor which is related to the ESR. It looks like some of those cheap LCR meters will provide ESR measurements above a certain capacitance. The better the LCR meter, the smaller the capacitance it will work on. \$\endgroup\$ Commented Sep 15, 2014 at 8:24