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Re: TC Inductance Formulas...

To: teslaatgrendel.objincdotcom

Subject: Re: TC Inductance Formulas...

From: "Malcolm Watts" <MALCOLMatdirectorate.wnp.ac.nz>

Date: Wed, 21 Feb 1996 09:46:20 +1200

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Hi everybody,
Replying to Timothy Chandler on this topic...
<big snip>
> L:(Average) (SUM) 0.166435839 166.43583937 166435.83937
> (AVG) 0.027739307 27.739306562 27739.306562
<again>
> L[m]:(Average) (SUM) 0.167945794 167.94579413 167945.79413
> (AVG) 0.027990966 27.990965688 27990.965688
<and again>
> L[p]:(Average) (SUM) 0.166568649 166.56864907 166568.64907
> (AVG) 0.027761442 27.761441511 27761.441511
I don't think you said what the measured inductance was (I may
have missed it.)
Comment  I too like exactitude but in the real world this is
physically not possible. All the science I know quantifies the
degree of uncertainty or experimental error. For example, the "end
effect" of a dipole aerial means that best tune is obtained with the
lessthanideally calculated element length. I suspect there are end
effects associated with coils as well and any coil will couple
however loosely into its surroundings. You will probably find that
slightly different formulae are needed to get the closest values for
different aspect ratios.
Last comment  if you are after accuracy in resonance measurement
use NO resistance, series or shunting with the coil. The following is
the "real" resonance formula :
fr = 1/(2xPI) x SQRT( 1/(LxC)  R^2/(4xL^2) )
I think I got that mouthful correct (I stand to be corrected). Anyhow,
by plugging the figures in you can see why the usual noresistance
formula is generally good enough for a quick and dirty ballpark
figure.
Further comments welcome.
Malcolm