From: "John Jardine"
Subject: Re: want a list of R value E6 E12 E24 E48 E96
Date: Tue, 12 Nov 2002 00:22:48 -0000
References: <3DCC0BE7.BEDAFF5@fanwap.com> <5wnbKyBajC09EwpE@jmwa.demon.co.uk>
NNTP-Posting-Date: 12 Nov 2002 00:11:43 GMT
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John Woodgate wrote in message
> I read in sci.electronics.design that John Jardine
> wrote (in >) about 'want a list of R value E6 E12 E24 E48 E96', on Mon, 11 Nov
> > Well go on then ... . I'm genuinely and honestly interested in knowing
> >the E() series were generated. There is scant info' out there and you may
> >the keeper of some interesting details. I think we should be told!.
> The values ARE logarithmic, or a geometric progression, in other words.
> NO BS. Not much to do with voltage dividers, though; more to do with
> tolerances. Just take a crude example, a 1.2 kohm +/-10% may be any
> value between 1.08 kohm and 1.32 kohm. A 1 kohm +/-10% may be any value
> between 0.9 kohm and 1.1 kohm. A 1.5 kohm +/-10% may be any value
> between 1.35 kohm and 1.65 kohm.
> Thus IF your circuit will accept a +/-10% tolerance, one of those values
> is bound to be OK (there is a small gap between 1.32 kohms and 1.35
> kohms, but you can't do better with just two significant figures for the
> If you actually calculate the values for the 10 % series, the ratio
> should be the 12th root of 10, 1.2115... So you can't get exact 2-figure
> values if you stick rigidly to that figure. The actual 'preferred
> values' deviate by more than just rounding in the case of 2.7, which
> 'should' be 2.6, 3.3, which should be 3.2, 3.9, which should be 3.8 and
> 4.7, which should be 4.6. It is alleged by a reliable author (Thomas
> Roddam in Wireless World) that the deviations were chosen to improve
> colour contrast. (The committee, IEC TC40?, obviously didn't think
> anyone would be ingenious enough to paint the resistor bodies maroon!)
> He also shows how to use the log properties (to bases other than 10) to
> simplify calculations of networks.
> Regards, John Woodgate, OOO - Own Opinions Only.
> Interested in professional sound reinforcement and distribution? Then go
> PLEASE do NOT copy news posts to me by E-MAIL!
Good info. (there -was- a committee then!)
The equi log spacing is what I had in mind. Nx12 (th) roots, will do nicely
for me. I had just seen Christian's reference and calculated a list of E24
values based on that sites offered 10% increment means. The results were in
the same ball park as established E24 but would require a *lot* of tweaking
on two asymptotes to make coincidence. I rather hoped that the earlier Mr
Lewis had some detailed knowledge to contribute but alas it was not to be
Should have guessed that T.Roddam had had a take on it and therefore is
*good*. Wish I'd never thrown my old W.W. copies away :-)