Hello,
This is my design for a 10k reference resistor.
It's based on a 9k9990 VHP202Z, plus a Thin Film resistor as a fixed trim. But I would recommend a 10k VHP101 instead.
It's sitting in a aluminum block, and this block is tightly attached to an aluminum case.
A precision NTC measures its temperature, so you can at first determine the R(T) curve and always precisely calculate its actual resistance at a given external temperature.
I omitted a PCB, due to leakage current, which created errors on the order of several 10 ppm.
The binding posts should be Pomona CuTe type 3770, as these have high isolation resistance, and low e.m.f..
If you use a DMMs with offset compensation, the binding posts can be of lower quality.?
4W Kelvin connection is required.
This assembly is good for 1ppm/year stability, real T.C. from 0.3 to 1 ppm/K (I got 5 of these), and a drift predictability meanwhile of < 0.2ppm.
So these can be used for calibration of a 3458A.
If you need other reference resistors, you'd need equivalent assemblies, but also transfer standards.
Frank
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