# Measuring the voltage of electrostatic machines

Discussion in 'The Projects Forum' started by DHodges38, Aug 5, 2010.

1. ### DHodges38 Thread Starter New Member

Aug 5, 2010
1
0
Hi; All

I have a 3.5" DIA. meter that has a 0-20 scale, the face of the meter reads as follows (KILOVOLTS D. C., 0-5-10-15-20, use with external resistor, weston electrical instrument corp. newark nj. usa, 1000Ω/volt, model 301, no).
I want to use the meter with a voltage divider so that it reads 1Mv full scale,so I can measure the output voltage of my electrostatic machines. I read the article titled Voltmeter impact on measurement, and the math on voltage dividers looks easy enough, and was planing on a 50:1 voltage divider. If I understand the article correctly that meter requires 1mA for full scale deflection,but these machines only put out 10's of μA.

My questions are:
1) Is this possible?
2)Would you put a 1kΩ resistor in series with the meter as the external resistor for the meter circuit?
3)Does this require an amplifier to measure voltages at the μA level?

This is my first post and I hope that I have made the problem clear enough for everyone to understand. Thank's for any help

2. ### nsaspook AAC Fanatic!

Aug 27, 2009
4,739
5,068
You need a Hi-Z HV meter for electrostatic measurements. example http://www.rossengineeringcorp.com/voltage_sensing_phasing.htm
http://www.rossengineeringcorp.com/hi-z_probes.htm

What you have is part of a older version of a common HV probe. Like these. http://www.rossengineeringcorp.com/hv_probes.htm

3. ### JDT Well-Known Member

Feb 12, 2009
658
87
Exactly. This meter is not sensitive enough for this type of measurement.

One rough way of measuring is to note that air breaks down at about 30kV per cm. So how large a spark can you produce?

The technical way is to use a electrostatic voltmeter that measures the force between two charged plates.

4. ### chriso New Member

Aug 6, 2010
2
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At school we used gold leaf electroscopes.