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Re: Measuring HV capacitor voltage (fwd)

---------- Forwarded message ----------
Date: Thu, 19 Jul 2007 01:21:24 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Measuring HV capacitor voltage (fwd)

Hi David,

A little while back I documented a hv divider:

I however broke one of the resistors and decided to simply buy some hv 
resistors and give them a try. I ordered from Allied Electronics p/n = 
296-0171 (the manufacturer is Ohmite who's p/n is EX2G1006). I just 
checked the website and it seems that part number is no longer listed? 
Odd. It's a pc board mount type. If you can imagine a 10 pin sip 
resistor with only pin 1 and pin 10 at their ends, this is what the 
resistor looked like. Was good for a hefty 10kV however. I think it was 
about 300M. It may not be available any longer? Anyway, something along 
that line can be used. You just have to alter the center voltage divider 
to suit.

Of course, the best way to measure is just to do an eBay search for a 
high voltage measurement probe for high "AC" volts. Their out there. A 
lot easier than building a divider and the cost is likely pretty similar 
in the end.

Take care,

Tesla list wrote:

>---------- 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