Hoi Ed,
On Fri, 28 Jan 2022 15:02:46 -0800
ed breya <[email protected]> wrote:
> I'm not familiar with the 3458A, so don't know how the connections are
> made up front. Presuming it's working right, I would suspect the
> interconnect setup. The thermal voltages and contact noise may be the
> main problem, especially using any sort of banana plugs.
These are not "any sort" of banana plugs. These are low-EMF from Pomona.
I doubt that wires would perform significantly better. But it's worth
a shot.
> Put the
> source current and high sense on one piece, and the low source and sense
> on the other. In operation, the Kelvin connections tie each twin lead
> pair together at the resistor, so even crappy insulation won't matter.
This I doubt. The effect I am seeing looks awfully like what I would
expect from a settling effect that takes a few seconds. And dielectric
absorption is one of those that are exactly in that time-range.
> Before changing anything around, a little experiment may shed some
> light. Instead of doing resistance measurements, set it to measure the
> voltage on the resistor, leaving the whole setup as it was. In the most
> sensitive ranges, with all those digits, I'd think you'll see the
> effects of the input bias current, the thermal voltages, and some
> resistor noise. The thermals should be easy to spot - just puff some air
> at the connections, or wave your hand around.
That's a good idea. I'll set it up next.
Attila Kinali
--
The driving force behind research is the question: "Why?"
There are things we don't understand and things we always
wonder about. And that's why we do research.
-- Kobayashi Makoto
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