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measuring the value of capacitor

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audioguru

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My multimeter can measure the capacitance of capacitors with a value higher than about 100pF. Below 100pf then the capacitance of the test leads and input of my multimeter add capacitance.
But usually I trust the value that is marked on a capacitor and the amount of tolerance that is also marked on it.

What is your ceramic capacitor marked?
 

MrAl

Well-Known Member
Most Helpful Member
Hi Anki,


To answer the question in a slightly different way...

It partly depends on what test equipment you have on hand and what
you intend to purchase in the near future.
If you dont have a meter that measures capacitance, then it is easiest to
get one that does, preferably one that has two slots in the meter face
where you plug the leads into the meter itself and dont have to use the
meter leads to measure capacitance, at least for smaller caps. For larger
values it doesnt matter as much.
If you instead have a scope around (lots of people do these days) you can
connect a resistor in series with the cap and drive it with a square wave
from a little generator you can build yourself, and measuring the voltage
at the center tap with the scope you can use equations like:
v2=v1*(1-e^(-t/RC))
and
v2=v1*e^(-t/RC)
to calculate the unknown capacitance, C.
This isnt actually that hard to do either, but yes you do have to have a scope.

If you happen to be into microcontrollers, you can pulse the RC network and
measure the tap voltage and do a few calculations to find the value of C too.

Another method involves using the C in a small oscillator circuit, then measuring
the output frequency of the oscillator and computing C from that.

Im sure there are lots of people here who would be happy to provide you with
a link or two to some circuits to do these things, if you are interested in
building your own capacitance meter.
 
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