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I bought a mixed bag of ceramic capacitors from Maplin and I'm struggling to identify most of them. I'm a bit of an electronics newb, but I understood that a capacitor usually has 3 numbers on and sometimes a letter at the end of the numbers. The third number indicates the amount of zeros you add to the first two to get the value in pF. Am I correct?

Well with that in mind, I introduce you to:

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The first one is a bit blurry, but it seems to have 8P2 printed on it. Next has n51 with Sy below it. The 3rd and 5th ones have a horizontal line under the number, and what might be a number one, or a corresponding vertical line, can't decide which it is. The 4th one seems a bit more clear now that I can see the writing more clearly in the picture - I assume this is 180pF? Finally the last one has 82 on it, is this simply 82pF?

Is there a way to test the capacitance at all? I have countless smaller ones with either blurry text, or nothing written on.

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Do you have a DMM with a capacitance setting, or an oscilloscope to do the measurement manually? – Kevin Vermeer Jan 17 '11 at 13:24

3 Answers

up vote 6 down vote accepted

8p2 = 8.2 pF

n51 = 0.51 nF

220 pF

180 pF

560 pF

82 pF

This gadget is useful for measuring low value capacitors (as well as inductors and frequency). I have a PCB design for it, if anyone is interested in building it.

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The rightmost cap in the top row looks more like "221" to me, so I'd vote for 220pF - I concur with the rest of your statements. – Madmanguruman Jan 17 '11 at 13:22
I think you are right. I've changed it. – Leon Heller Jan 17 '11 at 14:33
An LC meter that outputs in Morse code...right. I figured with the FCC no longer requiring hams to know Morse meant it could be pronounced dead once and for all :P – Nick T Jan 17 '11 at 20:45
up vote 5 down vote

The three numbers form, let's say XYZ(J), means XY x {10^Z} pF, e.g. 560 = 56 pF, 561 = 560 pF, 562 = 5.6 nF etc.

Cheap digital multimeters don't usually measure capacitances in this range, but you can build capacitance meter easily, there's plenty of schematics on the internet, just google "capacitance meter schematics".

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I found this page interesting, when I had similar problems.

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