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Ideas for measuring voltages of Tesla coils



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From:  John H. Couture [SMTP:couturejh-at-worldnet.att-dot-net]
Sent:  Monday, March 09, 1998 10:45 PM
To:  Tesla List
Subject:  Re: Ideas for measuring voltages of Tesla coils


  Jim -

  The methods mentioned below sound good but have the same problem as many
other methods. How do you calibrate the devices?

  John Couture

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At 12:49 PM 3/9/98 -0600, you wrote:
>
>----------
>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...
>
>
>