In message 19942e77-f4fd-4ba5-82cd-75a35bb5a...@gmail.com, Richard Moore writ
es:
Heavy gauge wire is only needed for current measurements, which I seldom do.
Heavy gauge wire has different thermal behaviour than think wire (area deepends
on radius squared, surface only on radius)
It
Randy — not sure why you feel the need for shielded wire for DC measurements,
especially if you turn the LP filter on, unless you live under a transmitter. I
use twisted pair 22 ga. solid copper bell wire for voltage measurments with no
difficulties, and the thermals reduce very quickly. Silver
Dick it is all in trying to get the last little bit of accuracy out of the
meter. 1000 NPLC and or math stat would do better than messing with the
leads... All this gets into the law of diminishing returns. 1 ohm test lead
in series with a 10Meg input resistance that only come into play on the 2
Randy — My 3458A manual specs 12 or 14 gauge solid copper wire for the short,
bunt in to a U shape. I use 14 gauge. Poul-Henning’s comments about thermals
are well-taken — even a simple folded up carboard shield helps. But I think
you’re near the limit.
I use a 8 oz styrofoam cup to isolate air currents around the 3458A terminals
when zeroing with shorting bar
Sent from my 20 Texas sized
iPhone
On Jul 27, 2015, at 2:57 PM, Richard Moore richiem5...@gmail.com wrote:
Randy — My 3458A manual specs 12 or 14 gauge solid copper wire for
I used a 12 AWG wire formed into a U shape for the short and the zero
voltage measured less than 0.2 uV after a good 2+ hour warmup. However, I
am seeing drifts of several uV for the 752 calibration. I was using TV
twin lead to connect the 732 to 752 and 752 to 3458A since that's really
all I
