RE: [VLF_Group] 100 GOhm resistor for ELF/ULF antenna buffer
- At 08:22 PM 2/29/2004 -0500, W1EOF wrote:
>Infinity-schminity... lol We regularly measure up to 10^12 (1 millionBob Pease from National Semi talks about Teflon a lot.
>megohms). It takes good equipment and careful procedures that's all. In the
>automated tester I designed back in the 80s we used an electrometer IC from
>Analog Devices in a picoammeter configuration. The feedback resistors were
>glass-bodied from Victoreen. Contanimation can be a problem, we used an
>industrial form of alcohol to keep it all clean. Next you start to have
>problems with stuff like triboelectric interference from your teflon
>insulators. It gets interesting!
It causes problems by storing charge internally. It's actually TOO good.
Glass and Air are your friends. :)
Everything in these circuits has to be kept more than surgically clean.
- Hi Wolf,
Ok on the spluttered film inside the bulb, I think that is a more
likely path rather than a water film outside the bulb. It was an
interesting thread for me even though it was a bit off topic, sorry
about that. But I have heard of at least one study trying to correlate
the fair weather field with world wide VLF spheric activity.
I found some 18G resistors on Ebay for reasonable $, but nothing
higher. I might see if I can pick up an old Keithly electrometer, it
could turn out to be cheaper than building something.