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Re: Measuring HV capacitor voltage (fwd)

---------- Forwarded message ----------
Date: Thu, 19 Jul 2007 17:08:49 -0500
From: resonance <resonance@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Measuring HV capacitor voltage (fwd)

I stock high megOhm resistors, rated 9 kV for HV measurement.  At 10 kV, 2
in series would work great when used with a 0-100 uA DC or 0-50 uA DC meter.
Contact me off-list.

Vishay, sold by Allied Radio, produces resistors pulse rated rated 1-10 meg
at 3 kV.  I usually derate them to 2 kV for a margin of safety.  This means
5 of these resistors would do the job at 10 kV.  Use a uA DC meter.  Also,
always use a string of anti-parallel 1N4007s (7 each way in series) across
the meter.  If the meter fails or the meter ground connection is broken, the
circuit across the meter will not jump to HV and can only hit the breakdown
resistive value of the 1N4007, usually 1.1 volts each, so the circuit only
jumps up to 8 volts.

At 100 kV we use 18 pcs of the 9 kV resistors in series --- don't like to
push them.

Another simple way to do it, assuming you are running a variac or something
in front of the 120 VAC xmfr, is just calibrate a 0-150 VAC full scale meter
to read 0-10 kV with the 10 kV hitting the mark just as the voltage hits 120
VAC indicated on the meter.  This simple meter recalibration is very
accurate due to your xmfrs fixed turns ratio, and all that is required is a
0-150 VAC f.s. meter reading 10 kV at 120 volts AC input level.

I have some 0-20 kV meters in stock.  Contact me off-list if interested.

Dr. Resonance

Resonance Research Corp.

----- Original Message ----- 
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, July 19, 2007 1:10 PM
Subject: 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?
> Thanks
> David Rieben