From: Spehro Pefhany
Subject: Re: what is 100R mean in a schematics?
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Date: Sat, 04 Jan 2003 17:43:11 GMT
NNTP-Posting-Date: Sat, 04 Jan 2003 12:43:11 EST
On Sat, 4 Jan 2003 16:22:12 -0000, the renowned "Zefram Cochrane"
>"John Woodgate" wrote in message > >Now, one
>of them was a tiny
>> That is 22 000 pF = 22 nF = 0.022 uF. The 'Z' describes the tolerance,
>> which is +80/-20%
>I've always wondered this: why are capacitor tolerances asymmetric.
>+80/-20% means a range of 17.6nF to 39.6nF. Why don't they just call
>it, say, a 28.6nF capacitor, with a tolerance of 39% or something ?
Those tolerances usually apply to electrolytic capacitors and some of
the nastier lot of semiconductor ceramic caps. In essence, they can't
make the cap that accurate and we don't really care that much about
the maximum capacitance that it might have, more about the minimum.
For example, for filter caps, if a 1000uF is actually 1500uF, no big
deal, but if it was 500uF it might cause problems. Same issue with the
bypass capacitors that are often ceramic types.
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