# Small ceramic disc capacitors

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#### woodturner550

##### New Member
I have some small ceramic disc capacitors that only give the code for their value. Nothing else, just the two or three digit code. How do I know what the voltage will be. Can't be much.

Some of the ceramic capacitors have a letter on them like 7E and the E means +/-.5%, which is a good close tolerance. Some have a 7P and the P means -0+100 %. Could you explame the "-0+100%".

Thanks for all the help with my education! I'm glad this is a hobby.

woodturner550

##### Well-Known Member
CAPACITANCE TOLERANCE
C = ± .25pF
M = ± 20%
D = ± .5pF
P = +100 –0%
J = ± 5%
Y = –-20 + 50%
K = ± 10%
Z = –-20 + 80%

So in the case of lets say a 100 pF (pico-Farad) capacitor with a P tolerance they are telling us the capacitor will be at least 100 pF (the -0%) but could be as high as 200 pF (the +100%). Unless we seek caps with a specific tight tolerance for a reason we can see caps like this aren't quite accurate as to value.

Ron

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#### woodturner550

##### New Member
Thanks Ron. That makes a lot of sense.

Now for the voltage part? How do I know what voltage they are acceptable for?

Thanks again.

##### Well-Known Member
Generally the working voltage is marked. When it is not present assume 500 VDC. However, the problem with caps like this is the forever changing guidlines. Literally it can become a crap shoot.

See the attached.

Ron

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• Caps.gif
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#### woodturner550

##### New Member
Thanks Ron. That confirmed my understanding of the voltage problem. Because I am working with voltages less than 25 volts always I don't have to worry about that. I am learning to program microcontrollers and connect various sensors and displays.

woodturner550

##### Well-Known Member
Something to consider is when you need a capacitor or design around a capacitor is to make sure the right capacitor is selected based on the application. Capacitors these days are a whole new science.

Ron

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