Moin,
On Wed, 9 Feb 2022 00:50:58 -0500
Illya Tsemenko <[email protected]> wrote:
> Any improvement on your 3458A results?
A bit. I now know what isn't the cause: The cable and EMF.
I found some silver plated, PTFE insulated AWG 30 wire (AlphaWire 2841/1)
and substituted it for the Pomona leads (Yes, not ideal, but that's the
only PTFE insulated wire I could find).
I did the same run of different NPLC, APER and DELAY settings as before
and the numbers are virtually the same. Additionally I also did a run with
APER 1 and larger DELAY numbers to see how that changes things (plot attached)
On some more long term measurement, the behaviour looks virtually the same.
There is no change that wouldn't be within the noise of the measurement.
I also covered everything in cardboard to shield it from all air currents.
While this inproved my temperature readings quite a bit (noise went down by
a factor of 5-7), it did not change the ohm reading noise at all (again,
all within noise/uncertainty).
But things are slow as the whole thing needs hours to stabilize. So each
time I change anything in the setup or the way how I measure, I let it
run for a couple of days to see what it did.
> I've got L&N 4040-10k resistor and logged it for a bit last night.
> This standard was just random ebay special, nothing fancy.
Coincidentally, that's the same type of resistor I am measuring.
> To mitigate tempco standard was placed in peltier active air bath,
> programmed at +23.00°C.
I whish I could do that as well, but my current budget does not allow
to buy a commercial air/oil bath and fire regulations prevent me from
using a home-brewn one.
> Overall noise of readout is within ±0.35ppm peak to peak.
That's about 1/3 of the readout noise I have for the same settings.
My current working hypothesis is, that the resistor has some significant
temperature gradient/change based behaviour, which would explain some of
the large jumps I see, which seem to be always around when temperature was
changing quickly (as in faster than 0.01-0.02°C/h).
I will further investigate and report back once I have a better understanding
of what is going on.
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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