General > General Technical Chat
100G -1000G Resistors
jonpaul:
OP: The combination you spec is impractical.
The tradeoffs of voltage coeff, R, precision at over 1 G Ogm are unobtainable.
We used Victoreen and Caddock in 1980s, on 12 kV Avaionics HV.
The 1000M were +/- 20%
Rated to 20 kV.
I would revise your approach to avoid the unreachable requirement.
Jon
Jon
magic:
By the way, I still don't know what you want to use this resistor for, but if it's just low level current measurement like in the article linked by Tim Fox then I don't see why you would need a 5kV rated part.
At first I thought you want it for a high impedance voltage divider or something like that.
PartialDischarge:
2kV is not that high, so you could use a follower opamp connected to the input and floating (bootstrapped) at the input voltage. Bandwidth is going to be high, but also is going to be the cost as you need a DCDC converter that gives 2KV although low current
strawberry:
2kV / 1Tohm = 2nA
jwet:
Magic- I explained as much as I could above. The box will measure voltages up 2500V with very light loading and measure very low currents (10e-14A) for their field techs that service Airport Ion Spectrometers- explosives detectors. Lab gear exists that can do all this but it has a lot of features that they don't need and costs about 4k and is not easy to source. They are doing a make/buy analysis to see if they can get something custom designed at 150 pieces for less than the cost of buying 150 $4K instruments, about 1/2 million and not really up to the task of knocking around in a tech's van. Their current solution is to FED-X a Keithley and an elecltrostatic voltemeter out to the field which is a pain too. This ultra low current, high voltage stuff is a funny niche that I did a while ago. I'm doing a 40 hour trade study right now to give them their options and they'll go decide. I'm only on the hook to deliver a study and this one of several avenues. I'm also looking at other consultants (better than myself) that specialize in this field. We'll see.
Thanks all.
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