Re: Measurement questions

["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 Weazle, 
  

Tesla list wrote: 
>
> Original poster: "J. B. Weazle McCreath by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <weazle-at-hurontel.on.ca> 
>
> Hello Coilers, 
>
> I took some measurements on my first coil, which I built long before I 
> was aware of this list and hence uninformed, and the results have me a 
> bit puzzled. 
>
> Some coil details first: 
>
> Top Load  - Sphere roughly 6" dia. (8.52 pF. from WinTesla) 
> Secondary - 3" x 13.5" of no. 22 (3.65 mH. from WinTesla) 
> Primary   - 7.5 turns of 1/4" tubing, spaced 1/4" with 
>             60 deg. conical! (.0086 mH. from WinTesla) 
> Capacitor - Glass & aluminum plates in oil (6 nF. measured) 
> Gap Type  - Two 1.5" disks spaced about 0.15" with fan 
> Power     - 10 K.V. -at- 23 mA. (one OBIT) 
> Frequency - 698 kHz. (from WinTesla) 
>
> Using Terry's method of finding mutual inductance I measured 
> a primary current of 9 amps and a secondary voltage of 110 
> millivolts across the 10 K resistor, 1 uF. cap as suggested. 
> If my calculator got it right then my M = 38 uH. or .038 mH.

Weazle, I haven't used WinTesla, but assuming WinTesla's values, then k calcs
to 0.183 wiht M at 32.4uH where k = M / sqrt (Lp * Ls). 
>
> Applying that figure plus the values of Lp and Ls from above 
> I get 0.2212 as my K figure yet WinTesla gives 0.75 as the K. 
> I expected to see a bit of a difference, but not that much!

There's something wrong there. If WinTesla is giving 0.75, then either the calc
is wrong or there is an input value entered wrong. 
>
> Could this be due to my extreme primary angle?  Like I said, 
> this coil was built before I knew the facts.  I didn't make 
> the same mistake (and others) on my subsequent coils!

No, if your measured amp and volt readings are good, then 0.75 has nothing to
do with the angle and more with calc or input. 

Take care, 
Bart