From: "Zefram Cochrane"
References: <email@example.com> <firstname.lastname@example.org> <email@example.com>
Subject: Re: what is 100R mean in a schematics?
Date: Sat, 4 Jan 2003 16:15:24 -0000
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"Chris Ainslie" <email@example.com> wrote in message
> Ok, on that note, I have a question....I'm not very clued up here!
> I was recently constructing a kit for an electric fence and the schematic
> told me where C3 and C4 should go and that C3 was a 22uF ceramic cap and
> was a 220uF ceramic cap.
> Now, one of them was a tiny yellow one with a shiny coating and had the
> number 224 on it. The other was one of those orange disc type ones with a
> matt finish and on it, it said 223Z.
> Can somebody explain the markings on these two caps for me.
Erk. Well, the "Z" in the second one is probably a tolerance, or
a temperature specifier: this is probably unimportant here.
Generally, you won't come across any "domestic" C or R
with more than two significant figures in its value. 223 means
"22 with three zeroes after it". "224" means, well you work it out.
"223" means "22,000" but 22,000 what ? Capacitors seem to
be to be in units of picofarads by default if no units are given.
So 223 is 22,000 picofarads, which is 22 nanofarads, which is
Your kit instructions seem to be wrong by a factor of 1000, but the
themselves seem to be correct. You will not very often find a 22uF or a
to be made of ceramic! Most likely, they were 22nF or 220nF, which is
consistent with the markings you are seeing.
22nF is 223, 220nF is 224.
Richard [in WR14]