Re: Awg formula, was "New formula for secondary resonantfrequency"

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>



Tesla list wrote:
> 
> Original poster: "Barton B. Anderson by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>
> 
> Hi Paul,
> 
> Thanks for taking a moment to spell out the calc. I made 2 errors. First was
> using log to base (of which I didn't specify) instead of the NL, and the
other
> was a decimal placement with wd (due to how I use the wd cell in an Excel
> sheet). Anyway, all is well. I now get 18.000447.
> 
> Thanks for clarifying the "Natural Log". If a base isn't specifically called
> out, Excel and calculators assume log to base 1. If you specified that in the
> text then I simply missed it. It's funny how the error came so close so I
> assumed the formula was entered correctly.
> 

Log base 1??? I suspect you mean Log base 10..

Just some general comment on all the discussion of wire gauges, which seems
to pop up on the list every couple of years. I've had some discussion with
the folks at MWS (a big supplier of wire) on the origins of the gauge
sequence, and tolerances involved.

The original source of the gauges was derived from pulling wire through
dies, and you go down one size for each pull through the die (originally...
now they do it in fewer steps, with more sophsticated equipment).  In any
event, the "idealized diameter" (without standard mfr tolerances, and
rounding)  follows a strict geometric sequence (i.e. the ratio in diameters
between successive sizes is constant).  These idealized sizes are then
rounded off to convenient sizes for manufacturing, and codified in some
ASTM (or BS, or whatever) standard.


1) Using a whole bunch of digits is probably superfluous, since the
manufacturing tolerance is around 1%.  If you take two numbers from a
published table and calculate the coefficients in the exponential formula,
the limited precision of the table means that your equation will inevitably
be off for other entries.

2) Every three gauges is approximately twice the cross sectional area
(another way of saying 6 gauges is twice the diameter)
(just like 3 dB is approximately twice the power, actually it's 3.0103... =
log10(2))

3) Every 10 gauges is approximately 10 times the area. 

4) AWG 10 is approximately 0.1 inch in diameter

5) Every manufacturer has slightly different sizes, and it varies with
temperature, tension, etc.

(Coefficient of thermal expansion) CTE for copper is 16.5 ppm/degree C...
you did take temperature into account when creating all those precise
equations, right?

I don't have the modulus for copper in front of me, but I'll bet the
tension has a distinct effect on diameter.


> >
> > Nope, the AWG sizes are fairly well defined, decreasing by a factor
> > 1.122932 with each step. This factor is the sixth root of two,
> > which means therefore that six AWG increments will exactly halve
> > the wire size.
> >
> > --
> > Paul Nicholson,
> > Manchester, UK.
> > --