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Measuring HV capacitor voltage (fwd)

---------- Forwarded message ----------
Date: Thu, 19 Jul 2007 15:15:51 +0000
From: David Rieben <drieben@xxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Cc: drieben@xxxxxxxxxx
Subject: Measuring HV capacitor voltage

Hi all,

I'm having a little issue with measuring up to 10 kV across a capacitor
on a standard panel mount, analog 0-15 VDC voltmeter from Radio 
Shack. Obviously, I was trying to make it read 1 volt for each measured
1000 volts. I tried using a voltage divider of 10 seriesed 10 meg resistors 
and a 100 K pot but found that the 100 megs was just too much resist-
ance to allow for sufficient current for reliable movement of the volt meter. 
I then tried a series-parallel arrangment of 10x10 of the 10 meg resistors 
for a total of 10 meg and then still used the 100 K pot and varied it to try 
to bring in the proper calibration. I was checking the voltage measurement 
with my HV probe and DVM. The resistors didn't like being bunched up 
10 at a time and started flashing over externally. Also, I was having trouble 
getting the analog meter readings to be accurate throughout the 0 - 15 volt 
range according to the measurement of the HV probe. I think the meter is
designed for 10 meg impedance and it also comes with a 15 K resistor that
is supposed to be in series with the voltage source. Anyone have any sug-
gestions for reliable and reasonably accurate measurement of high voltage
through a low voltage analog voltmeter via a voltage divider network? 

David Rieben