Advertisements

Relics of the Empire: Electrometer Resistors

From Russia, probably without love, routed through Bulgaria via eBay:

Electrometer resistors - wrapped

Electrometer resistors – wrapped

They’re glass electrometer resistors from late in the Cold War:

Russian 100 G electrometer resistor

Russian 100 G electrometer resistor

That one presents 100 GΩ between its lead wires, which would count as open in any other circuit I’ve ever built.

The assortment arrived much richer than advertised, although I’d be even happier with a few more 10 GΩ and a few less 100 MΩ resistors. The 1000 GΩ = 1 TΩ resistor in the upper right seems absurd on the face of it, but there it sits.

I have no way to measure these, other than to build an electrometer amp and see what happens…

Advertisements
  1. #1 by madbodger on 2015-07-30 - 07:55

    I’ve been known to use 10MΩ resistors as standoffs. These are a whole ‘nother order of magnitude! I imagine you have to keep them clean for them to maintain their characteristics. I might try to measure them with a leakage detector, or perhaps a kilovolt power supply with one of these in series with an ordinary DVM. With the 10MΩ input impedance, they’d make a workable voltage divider.

    • #2 by Ed on 2015-07-30 - 12:42

      Let’s see: 1 kV across 100 GΩ in series with 10 MΩ gives you, uh, just under 10 nA and 10 whole millivolts!

      I’m pretty sure I could get a number, but I wouldn’t trust it at all… [sigh]

      First time I’ve had to run numbers like those, for sure.

  2. #3 by steve on 2015-07-30 - 11:02

    A co-worker showed me a 1TOhm surface mount resistor… I wondered if the air between the pads was more conductive.

    • #4 by Ed on 2015-07-30 - 12:22

      That’s just crazy talk: without absurd precautions, PCB leakage presents a lower resistance!

      Breathing on the poor thing would certainly affect the results…

  3. #5 by Glenn on 2015-08-06 - 04:01

    These resistors can be measured using a GR 1864, I have one, very useful.
    http://www.ietlabs.com/genrad-1864-megohmmeter.html

    • #6 by Ed on 2015-08-06 - 07:34

      And it goes up to 200 TΩ!

      If the resistor could withstand the meter’s full 1 kV, it’d carry 5 pA. Heck, that’s almost enough to see with your naked eyeball!

      Now that you mention it, Eks probably has a megger in his collection…