Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!ub!kitty!larry
From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics
Subject: Re: A conundrum about the AWG (wire gauge) table
Summary: Yes, Virginia, there *is* a rationale behind AWG... :-)
Message-ID: <3981@kitty.UUCP>
Date: 29 Aug 90 13:44:08 GMT
References: <2588@ryn.esg.dec.com>
Organization: Recognition Research Corp., Clarence, NY
Lines: 27

In article <2588@ryn.esg.dec.com>, jroth@allvax.dec.com (Jim Roth) writes:
> Many of the standard values in electronics and elsewhere follow an
> approximate log/exp scale to accomodate a wide range of values.

	There were no "electronics" at the time that the American Wire
Gage (AWG) was created.  The AWG was formerly called the Brown & Sharpe
wire gage.  Offhand, I cannot give you a precise year of origin, but I
would guess around 1875, +/- 10 years.

> Wire gauges are no exception, but here's an odd thing - virtually
> none of the diameters or areas in circular mills are "round numbers".

	That's because they are *not* round numbers!  The rationale
behind AWG is that the ratio between DIAMETERS of succesive gage numbers
is 1.123, with the ratio of areas therefore being (1.123)^2, or about
1.26 (remember about 1-1/4).  I have no idea why this ratio 1.123 was
chosen.

> Yet when we take logs, we find that each jump of 10 wire gauges
> increases the cross sectional area of the wire not by a nice round
> number like 10, but by about 10**1.007!

	Hey, that's pretty *close* to 10, though. :-)

Larry Lippman @ Recognition Research Corp.  "Have you hugged your cat today?"
VOICE: 716/688-1231   {boulder, rutgers, watmath}!ub!kitty!larry
FAX:   716/741-9635                  {utzoo, uunet}!/      \aerion!larry