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Em 05/02/2016 02:08, Ed escreveu:
Warning to all:
Be very careful with any meters around a VDG because of dangers
from sparks. DMM's are very easy to damage and regular panel meters
are too. I always shunt DMM's with 0.1 ufd capacitors even if it
makes them slow readings. Panel meters are best protected with a pair
of rectifier diodes across the terminals, one with polarity reversed
so that the pair conducts in either direction. I had a very valuable
0 to 5 uA panel meter which I blew open with a spark before I found
out the danger.
I had problems in two situations. One, measuring current at a
high-voltage without taking care to properly insulate the meter, that
was damaged by sparks through his case. Another, this quite silly,
measuring current to ground. After some measurements, I turned off the
system, and the meter too. When I returned to make more measurements, I
turned on the system with the meter still off. It was destroyed by
internal sparking.