TSSP: List Archives

From: "Mark S. Rzeszotarski, Ph.D."
Date: Wed, 29 May 2002 10:52:59 -0500
Subject: Re: Top V Probe Design (was RE: [TSSP] Topload breakout

Greetings Bert and All:
At 07:46 AM 05/29/2002 -0500, you wrote:
>Hi Malcolm,
>
>This could work in principle, but I think a larger amount of capacitance
>would be desirable in practice to reduce AC ratio errors introduced by
>the stray capacitance between voltage grading toroids/rings and to the
>surrounding secondary winding. I'd think that we'd want to keep the
>capacitance between successive stages at least 100X as large as the
>parasitic capacitance to reduce the effects of capacitive coupling from
>the surrounding secondary.

>>               It occurred to me last night that if the central
>> divider chain were to be a compensated RC ladder, it might be
>> possible to make a resistive chain self-compensating by using the
>> stray capacitance between resistors. Essentially, by arranging the
>> resistors in the following fashion:
>> 
>>   |
>>    ---///--
>>               |
>>    ---///--
>>   |
>>    ---///--
>>               |
>>    ---///--
>>   |
>> 
>> etc. and suitably sizing the resistors such that their resistance
>> matched the parasitic capacitive reactance, we might obtain such a
>> result.

        Looking at my High Voltage Engineering text last night, I see that
the big boys are using deionized water doped with CuSO4 in PVC tubing as the
resistor with the tubing spiral coiled to distribute the capacitance and
corona effects.  They claim bandwidths on the order of 100 MHz with their
systems (used to look at impulse/step responses similar to our pinger
experiments).  Also, 1000:1 is not near enough ratio for a live coil.  I
would shoot for 500,000 top volts dropped to 5 volts or a 100,000:1 divider
ratio.
Regards,
Mark S. Rzeszotarski, Ph.D., Assistant Professor of Radiology and Biomedical
Engineering, Case Western Reserve University, Cleveland OH USA


Maintainer Paul Nicholson, paul@abelian.demon.co.uk.