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Re: Ctop Measurement vs. Calculation

Hi Bart,
             Trying to get a figure for a terminal above the coil is a 
really nasty business as even the lead wire going up to it contributes.
Same deal with an "isolated sphere" (like just how isolated is it with a 
signal/measuring wire going to it?).  The whole business is full of 
fish hooks. Tesla tried this at Colorado Springs and ended up with 
some pretty dodgy figures. I've had similar problems in the past. 
You can't stick a source inside the sphere and hope for a clean 
measurement of the e-field on the outside either since the sphere 
now has what amounts to an inner plate.
      BTW - raising and lowering the terminal above the coil is a great 
way of fine tuning without having to mess around with the primary if 
the primary tuning is close enough to begin with. 

Regards,
Malcolm

On 23 May 00, at 5:53, Tesla List wrote:

> Original Poster: "Barton B. Anderson" <tesla123-at-pacbell-dot-net> 
> 
> Hey guys, 
> 
> Terry - thanks for running E-Tesla5 and plotting the graph. It's been a
> while since I've used your program. I did it a long time ago with my coil
> back in MN. Took forever on my snail pc. I think I'll do it again with my
> latest test and check the results to my measurements. I am presuming the C
> output of 30.5pF was the resononator C. This would work out almost perfect
> to my calc of 9pF for the sphere from the frequency measurement. 
> 
> Tonight I placed the sphere on an insulated column, but couldn't stop
> breakout, even insulating the wire from the top of the secondary through a
> horizonal pvc pipe to the sphere. Breakout just screws up any possible
> measurement on the scope. But, I did raise the sphere 18.5" and retuned for
> 0.02uF. The sphere was 26.5 inches above measuring from the horizontal
> center of the sphere to the secondary top plane. The frequency was now
> 89.3kHz bringing Ctop to 14.7pF. This is quite a jump for the sphere being
> raised only 18.5 inches. My tuning is off some but I think the test shows
> significant change (40%!). The overall C changes then by 16%. 
> 
> I am really amazed at the amount of change here. As Malcolm and John
> pointed out, if the top terminal is too small in relation to the secondary,
> the secondary can swallow it up. Since my sphere is only 2 inches wider
> than the secondary around the perimeter, then this may be the leading cause
> of capacitance drop for this setup. 
> 
> I'll do the same test with my two toroids which should not be swalled up as
> much - about 2.7 times larger than the secondary diameter. 
> 
> Bart 
>  
>