Ideas for measuring voltages of Tesla coils

To: "'Tesla List'" <tesla-at-pupman-dot-com>
Subject: Ideas for measuring voltages of Tesla coils
From: Tesla List <tesla-at-stic-dot-net>
Date: Mon, 9 Mar 1998 12:49:06 -0600
Approved: tesla-at-stic-dot-net

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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...