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. =)
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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