I'm trying to measure the leakage current along an insulator energize with HVDC (the effect of space charges is been considered).
- Can I connect a picoammeter to the ground electrode? If yes, please how do I protect the picoammeter so as not to damage it?
Or
- Can I connect a voltage divider (with 5kohms and 50ohms connected in series) at the ground electrode, measure the voltage across the 50ohms with a picoscope and from there I can use V=IR to get my current? If yes, please how do I protect the picoscope from getting damaged?
Thanks.
It is preferable to avoid ohmic connections by resistances. I propose to use a follower Aop (high impedance input amplifiers) to measure the current.
Thanks for all these answers.
But what about going with the second option and connecting a Zener Diode in parallel to the picoscope, can it work?
Please note that this is a very high DC voltage (up to 250KV).
okay, Something like the picture attached.
R1=5kohms , R2=50ohms the picoscope has an internal resistace R3=1Mohms and internal capacitance C1=13pF and the limits of its input are -20V to +20V.
So I'm thinking again, what if I connect a zener diode accross R2, can it protect the picoscope?
Thanks
I know of industrial applications in Aluminum industry where they use hall effect transducers are used in clusters of parallel circuits for measurement of high current DC. We may use cluster hall effect transducers in series to to connect a picoammeter. It would provide the desired isolation.
Regards,
A zener diode will conduct some current (effectively lowering the value of R2 in some non-linear way). If you are aware of that - and eventually run some calibration routine to evaluate the measurement error - it may be viable to do so.
If it's really about pAs, even a 'normal' diode (resp. 2 diodes - connected anti-parallel and parallel to R2) should do. Not sure whether the picoscope will give usefuo readijs at such low voltages...
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