Re: [TCML] voltage

[Jim Lux <jimlux@xxxxxxxxxxxxx>]

On 1/25/12 9:54 PM, jhowson4@xxxxxxxxxxx wrote:
> This actually sounds like a moderately good idea. But we should go about it in a slightly more scientific way.
>
> I would be willing to bet that with the combined efforts of some list members, we can produce a "box" that contains the stuff needed and instructions on how to accurately measure the voltage of a particular coil. Pass the box around, and in a few months we should have tons of data. Data which could be correlated based on coil input power, physical characteristics of coils, frequency of operation etc. Match that data up with a maximum spark length each particular coil could produce. and we should now have a pretty close model of voltage to spark length characteristics . maybe some fancy graphs to show the world.
>
> This would require team work, I for one would be up to participate. =)
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> I mentioned this earlier, but i don't see why a huge voltage divider would not work, since we all seem to be interested in spark lengths relation to voltage.
> tons of resistors, in a wax or epoxy filled pvc pipe, mini toroid on top, a little tripod to set it up. Ground one end let the farthest spark hit the other, rectify and filter the last resistor and measure the peak voltage. I have done something similar before with my mini coil a long time ago, way long ago, before i really even knew how to make an actual coil.

THis is pretty tricky.  A HV divider (for RF) needs to carefully manage 
the capacitance as well as the resistance.  In fact, if you don't need 
to measure DC, a capacitive divider works better, and is easier to 
construct.


 And, consider that you don't want corona, or other weird effects, so 
you need to design for, say, 2 MV, which means radii of curvature of the 
HV terminal is going to be at least 60cm.  A 4-5 foot sphere is pretty big.


But, as a practical matter, the subject of HV dividers (even up into the 
megavolt range) is pretty well covered in the literature.


But, to a certain extent, that's what Terry's efield probe is.  The 
upper capacitor (in the divider) is from topload to probe, the lower 
capacitor is the probe to ground. You just calibrate it in-situ, because 
it's difficult to know what the C is between top load and probe.



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