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

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Jim, 

Yea, I was waiting for someone to point out the tolerances. Your absolutely
correct and applies to all awg size formula's. However, in programs, it's nice
to use a simple calc rather than a lookup table and it's nice to have the user
enter the awg size for the remaining calcs.  I used the formula in my rendition
of Ed Sonderman's Excel spreadsheet, however, JavaTC has the user input the
wire size and gives a pop-up table of standard sizes and winding tension. This
way, the user can input a measured value if so desired (something that should
work for everyone - that's the goal anyway). 

But, yea, your right on all accounts and something all coilers should be aware
of. All the various programs get us real close, but they are only programs used
to aid the builder, and these subtle variations will affect something slightly
different than what a program identify's. 

Take care, 
Bart 

Tesla list wrote: 
>
> 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. 
> > > --