On Wed, 22 Aug 2007 12:38:15 -0400, "Michael A. Terrell"
wrote:

rex wrote:

I agree on Fluke robustness. Pretty much the same story with my 8520A
bench meter.

I wanted to make my own high voltage probe. At a flea market I had
aquired some glass encapsulated resistors that were multi-megohm. I
thought they would be perfect for my probe divider, so I built one in a
plastic tube. Tried it at some hundreds of volts and it seemed to be
working as expected. I applied it to something like 1700 V. The tube
was clear plastic, and to my horror the resistor lit up with plasma and
ugly clicking noises came out of the meter. Looking at the meter, the
fluke display had switched to Klingon or something. Expecting disaster,
I power cycled the Fluke. It came back to life and was fine.

That resistor still baffles me. As I said it was in a glass tube and was
at least an inch long. It looked perfect for HV. My guess is that it was
filled with some gas to deliberatly short itself at some voltage in the
low KV range.


Did you clean all body oil and other contamanints from the resistor
before you used it? A single fingerprint on a one inch glass HV
resistor could cause arc over, and for it to self destruct.

It clearly arced inside. It looked like a neon tube not a simple
arc-over. The voltage I was measuring should not have come anywhere
close to arcing across that length. That's why I'm thinking it was
designed to do that. I looked for the resistors yesterday to see if I
could find markings, but I can't find where I stashed them now.