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Old 30th January 2011, 09:50 AM   #21
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Quote:
Originally Posted by kavermei View Post
I once saw a 10Gohm or so resistor which was encapsulated in a vacuum glass tube... To keep moisture out...
VICTOREEN used to make these.

I have some 1GR 1% in my standards box.

Now made by ohmite I think
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Old 30th January 2011, 03:40 PM   #22
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Electronic Surplus still has some Victoreen parts:

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Electronic Surplus was only a few miles from the Victoreen plant and would often have surplus parts.

We purchased some of those vacuum glass tube resistors from E.S. they may still have a few.
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Old 31st January 2011, 11:16 PM   #23
tomchr is offline tomchr  United States
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Originally Posted by Doz View Post
Yep, spill the beans ... what's it for?
Hello?! What's this for? I'm curious cat here too...

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Old 31st January 2011, 11:44 PM   #24
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Originally Posted by johnferrier View Post
OP is in Denmark, I think but . . .

$5.50 w/expedited shipping five available



ebay: New Vishay FHV-150E-1G00FK 1 GIG 1.5 WATT 1% 100 PPM thick film resistors


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Lets see. It would take 39 KV to make 1.5 W in a 1G ohm resistor. I just can't imagine what a 1G ohm resistor would be used for.

Bobby Dipole
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Old 1st February 2011, 12:24 AM   #25
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One use is to measure leakage currents in the nano amp range.


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Last edited by johnferrier; 1st February 2011 at 12:29 AM.
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Old 1st February 2011, 12:35 AM   #26
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Quote:
Originally Posted by Bobby Dipole View Post
I just can't imagine what a 1G ohm resistor would be used for.
For audio, not much. But it is a common size for range divider networks in high impedance electrometers. Also for sensitive current amplifiers as well as range resistors in megohmmeters. Older Geiger counters use very high megohm resistors on their inputs. Generally on the order of 50 gigohms and up. These were the glass encapsulated types that Victoreen made.
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Old 1st February 2011, 02:10 AM   #27
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As said before: just buy one.

Re: what would they be used for? I worked on a product that used a piezo-crystal sensor (inherently AC and capacitive), but they wanted near DC response; so we used the sensor in the feedback loop and the 1 Gigohm resistor as the input resistor IIRC.

Problems: Our resistor was surface mount, and I used lots of alcohol and maybe freon cleaner to make sure it was clean of flux (mostly underneath). Then we encapsulated the whole circuit to avoid humidity effects. We shielded it to avoid responses to static electricity. Something, probably the op amp, was also photosensitive, but the shielding and encapsulation eliminated that issue. All said, it wasn't that bad, if you need it - do it. If you don't need it - then avoid it.

Last edited by benchtester; 1st February 2011 at 02:17 AM.
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Old 1st February 2011, 06:05 AM   #28
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Mouser has them up to 1T. The 1G at 2KV is only $1.50.

Vishay Data Sheet

The 1T will cost you $300.

Last edited by Captn Dave; 1st February 2011 at 06:08 AM.
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Old 1st February 2011, 06:58 AM   #29
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Quote:
Originally Posted by benchtester View Post
Something, probably the op amp, was also photosensitive,
Wow! Do you mean high energy photons or even UV and visible light?
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Old 1st February 2011, 09:17 AM   #30
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Interesting with the 1/10 watt power rating. That indicates a voltage of 316kV. The plot thickens...
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