Measuring High Voltage Electrostatic Currents

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.

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.

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.