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Ideas for measuring voltages of Tesla coils
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From: D.C. Cox [SMTP:DR.RESONANCE-at-next-wave-dot-net]
Sent: Monday, March 09, 1998 6:51 PM
To: Tesla List
Subject: Re: Ideas for measuring voltages of Tesla coils
to: Jim
We made a field mill generating voltmeter a few years back and drive it
with an 1800 RPM synchronous motor. You are correct -- the measured peak
potential from a resonance transformer is in close agreement with our
measurements using x-rays to determine the peak output potential. We used
a 150 kV power supply to calibrate the TC by applying this to the HV toroid
with the wire connection removed. It works and the field mill meter is
relatively easy to make. Machining costs are relatively low -- only
required to cut out precisely the "butterfly wings" required for a
sinusoidal output although this is not really necessary with short duration
pulses. We also use this machine to calibrate the output potential on our
VDGRF generators.
DR.RESONANCE-at-next-wave-dot-net
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> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-pupman-dot-com>
> Subject: Ideas for measuring voltages of Tesla coils
> Date: Monday, March 09, 1998 11:49 AM
>
>
> ----------
> From: Jim Lux [SMTP:jimlux-at-earthlink-dot-net]
> Sent: Sunday, March 08, 1998 5:53 PM
> To: Tesla List
> Subject: Ideas for measuring voltages of Tesla coils
>
> While researching some electrooptical phenomena for fast shutters, I came
> across a reference to using the Faraday rotation in a chunk of lead glass
> to measure the current in an EHV transmission line. A basically optical
> technique, it draws no power from the signal being measured, and is
> inherently insulated.
>
> This got me thinking about measuring the voltage and waveform of a Tesla
> coil using some E-field dependent phenomena, namely the Kerr and Pockels
> effects. Both of these cause the polarization of light to rotate when the
> active area has an electric field across it. So, an active cell, a couple
> of polarizers and a light source/detector combination and you have an
> isolated E-field probe. By traversing over a path from the topload of the
> TC to ground, you can integrate the voltage and get the total voltage.
>
> Not only that, but the Kerr and Pockels effects are very, very fast
> (picoseconds), so you can actually see the waveform.
>
> Since all the optical components are insulators, it won't perturb the
field
> much. You could either use fiber optics to get the light to/from the
cell,
> or a laser and some mirrors.
>
> More details on the measurement techniques at
> http://home.earthlink-dot-net/~jimlux/hv/eo.htm
>
> Comments, anyone? Seems like this gets away from all the problems of
using
> spark gaps, voltage dividers, etc.
>
> Another "non-invasive" technique might be a field mill or other
> electrometer scheme, although I am not sure I would want to put one close
> to the arcing range...
>