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Join Date: May 2008
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Measuring High Voltage Electrostatic Currents

10/01/2008 1:00 PM

Hi Guys,

A colleague of mine has asked me to help him with his experiments, but there is an area which is outside of my current knowledge base that I need help with, so I came to ask the experts.

My friends experiment operates at high voltage from 7-15kv, in the future maybe even higher. He wants me to measure current flow in the field. He estimates that the current will be between 1*10^-9 and 1*10^-12 Amperes, so we are talking nano and pico Amperes. Anyone know an easy way or any way to make these kinds of measurements?

Any method would be helpful.

Thanks

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Guru
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#1

Re: Measuring High Voltage Electrostatic Currents

10/01/2008 1:32 PM
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#2

Re: Measuring High Voltage Electrostatic Currents

10/02/2008 6:56 AM

We have to measure microamps at up to 30kV, normally this is done by dedicated bench power supplies which display the current but, our engineers tell me that they can measure the current using a DVM like this 149 series but using the voltage range with a high resistance shunt across the input. They did say that the whole meter has to float up to the H.V so it must not be grounded.

Don't ask me to explain the calculation as I am only a simple mechanical engineer.

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Commentator

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#3
In reply to #2

Re: Measuring High Voltage Electrostatic Currents

10/02/2008 7:42 AM

Thanks I'll give this some thought. My power supplies like yours can measure the current down into the micro amperes, but my friend is looking for measurements in the nano and pico ampere at high voltage which is what makes it difficult. These kinds of measurements are a breeze at low voltage, but in the Kv scale they are next to impossible it seems like.

I appreciate your advice.

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#4

Re: Measuring High Voltage Electrostatic Currents

10/02/2008 9:02 AM

For years, ESP field secondaries have been measured with resistance elements. Using a voltage divider network to measure voltage and a feed back resistor to measure current. For the high voltage divider, 150 to 200 MΩ, 100 kΩ, 100 kΩ. For the current sense, use a resistor on the ground return, about 5 Ω for an amp, less resistance for smaller current. Many companies, world wide, make controls for high voltage electrostatic precipitator applications, these companies have off the shelf components to make the measurements you want to make.

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