General > General Technical Chat
100G -1000G Resistors
jwet:
Looking for very high value resistors- 1 TOhm ideally with a 5kV rating, <=1/4w fine, <=250 ppm/C and decent voltage coefficient. I can stack a couple but the capacitance quickly gets out of hand. I plan to air wire this stuff on Teflon standoffs but don't want to resort to anything more exotic. The application is high impedance voltage measurement around 2kV nominal- consulting job.
Stackpole, Murata, and Ohmite make the kinds of parts I want but they appear to be unobtanium or are $100/unit. Victoreen, Cleveland used to make parts like this but they got bought by Fluke and I can't find them anymore- maybe internal use only. New Old Stock in decent shape would be fine if they can provide 100'+s. One time build of a few hundred units is most likely. I've looked on Ebay and see some very old NOS Russian/Bulgarian beauties from early cold war, probably 70 years old. Qtys are low but am asking suppliers, will buy some to test with. The Bulgarian units are sealed in glass, tolerances are loose (5-10%), no specs other than ohms and quantities are limited (so far). Does anyone have any experience with these- photo below. They're about $5 in singles which is in the ball park. I used to get these from Victoreen for about $1.
Any other suppliers, leads or ideas would be appreciated.
Benta:
Did you try Vishay (didn't check myself)?
TimFox:
The Bulgarian unit shown is very similar to the older Victoreen deposited-carbon, sealed-in-glass units that were used in systems such as Keithley electrometers.
I'm not sure they were rated for 5 kV.
A modern source for 5 kV units is Ohmcraft https://ohmcraft.com/wp-content/uploads/2022/02/HVR-datasheet.pdf but I don't know their pricing or minimum order.
jwet:
Thanks- funny you should mention Keithley- another Danaher, Tektronix, Fluke, Victoreen, Fortive? head spinning acquisition circle. As a Maxim FAE, I used to love going to Cleveland for Victoreen, Keithley and AB/Rockwell - I did several studies of industrial electronic companies and Cleveland was ground zero- great products and engineers.
Did Keithley make those resistors in house? Victoreen had them made by Dale/Vishay I think but also sold them as components to get their volumes up to where Vishay cared.
wraper:
--- Quote from: jwet on May 13, 2023, 09:19:54 pm ---The Bulgarian units are sealed in glass, tolerances are loose (5-10%), no specs other than ohms and quantities are limited (so far). Does anyone have any experience with these- photo below.
--- End quote ---
This is not Bulgarian but Soviet and has datasheet.
https://www.quartz1.com/price/PIC/480Q0717900.pdf
http://www.155la3.ru/datafiles/kvm_kim_klm_tu_1977.pdf
You can google translate it and ask if something is not clear, I speak Russian. КВМ are vacuum composite resistors. +1000/-2000ppm/oC TC, -60/+85oC, 100V max. Rated to drift not more than 30% during 10k hours of operation and not more than 25% during 12 years of storage.
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