18 Jun
2013
18 Jun
'13
1:32 p.m.
On Tue, Jun 18, 2013 at 07:00:47PM +0100, Tony Duell wrote:
Another convention, used on the components themselves,
is to give the
value as a 3 digit number -- 2 digits and a power of 10. So that, for
example,. '472' means 47*10^2 = 4k7 (if a resistor). Very common on
surface mount components.
That's certainly OK with me (except when they lie, as you say), since it's
just a numeric version of the Bad Boy colors which have always been nice
(I like picturing whatever machine paints the stripes on resistors). What
puzzles me is why SMD resistors pretty much always have the numbers, and
SMD caps pretty much never do.
I was mainly confused by my 2R2uF because it *also* said "uF". And really
I'm surprised to see anything but "2.2uF" on something American-made
that's
that old (1980ish) -- it only missed "2.2mfd" etc. (OK I admit mmfd is dumb)
by a decade or two and it feels to me as if that 4K7 stuff is fairly recent
in the US (it seems to go hand-in-hand with drawing resistors as meaningless
rectangles instead of as righteous zig-zags). But maybe that's just because
I don't read trendy enough magazines.
Still, I can't believe that the CAD software I use doesn't even *have* omega
or mu in the default silkscreen character set. It's Australian -- is that
why? I mean, electronics are the one place where even the US has always been
metric and it *still* keeps changing on us!!! Harumph I say.
John Wilson
D Bit