RE: New Inductance Formula

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

Original poster: "David Thomson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>

Hi Terry, these messages I'm sending to you didn't go through today.

Hi Bart,

>Well, I tried your formula but am getting a value of 37837. If this is mH,
then it's way off, but maybe I've made a boo boo. Therefore, here's my flat
coil measurements. Do the your math and let us know what you come up with.
My L meter is the Wavetek 27XT.

Did you use 2.112 x 10-4 for conductance?  Also, the power of ten should be
10-4 in the denominator.  The formula is easier to see at the web site.
Also, be sure to enter WIRE length and not WINDING length.
http://www.tesla-coil-builder-dot-com/inductance.htm

>"All" values "measured":
298 turns
0.0225 total wire diameter (.0201 bare)
13.9775 OD
0.625 ID
13.8 ohms
11.9 mH

>For what it's worth, Acmi predicted 12.0mH and JavaTC predicted 11.8mH
(Wheeler). From my inductance measurements and from my perspective, I am
unable to ascertain why there's an issue.

I came up with 8.419mH based on a calculated wire length of 1090.511 ft.
How much of a pig tail is on the coil?

Keep in mind, my thought is that this formula calculates inductance for the
coil at resonance.  Static measurements will necessarily be higher in a
solenoid coil due to the impedance of the coil at the frequency it is being
tested at.  I'm not saying the full amount is impedance, though.  It is
quite possible that the formula may still need to account for something else
such as wire gage, molecular material, or some other characteristic of the
coil.

I'm just excited that it produces a close number AND in the correct units.

Thanks for your feedback.

Dave