Electronics > Beginners
Capacitor Tolerance?
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MikeSW17:
Is it always (usually?) best to use a close tolerance capacitor?
Put another way. I like building electronic DIY kits, I usually meter the components as well as checking the markings.
I know my metering device is probably crappy - but it does give consistent results on repeat tests of a given capacitor.
What I'm wondering is, if I have say a few 100pF ceramics in a kit and they measure say between 87pF and 112pF, is it worth me digging through my general stock for, say caps between 95pF and 105pF (or better)?
I'm sure the answer will be 'it depends on the circuit'; I know that say a RC filter or oscillator will be more accurate with high tolerance parts.
But more generally does 10-20% tolerance really matter given that the designer should have accounted for expected variances?
I guess the question is, what do other people do; go with all caps (etc) supplied as is (obviously not using and real duds) or try and 'better' the circuit?
Brumby:
Absolute accuracy of value - a.k.a. tolerance - is not a big issue in quite a lot of cases. What is often more important is stability - that the value doesn't change with environmental conditions and age, but the importance of that also depends on the application. Reliability is another factor.
If you have a few 100pF ceramics, I wouldn't be worrying about measuring them for the sort of applications in which they tend to appear.
Kleinstein:
For quite some applications the tolerance (and stability) of capacitance does not matter. Examples are power supply decoupling and AC coupling caps.
As low tolerance caps are rare one usually tries to avoid them and if really needed, there should be a note on the caps to use.
There are a few circuits that like matching caps (e.g filters with differential amps).
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