Electronics > Metrology

Homemade resistance standard

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mojoe:
I ordered a couple of Vishay Z-foils resistors from Mouser. They don't have much of a selection. I ordered one 100 Ohm and one 10K to make my own resistance standard. I'll be using the Pomona low thermal EMF binding posts. Since I'll be using Kelvin clips on the DMM, I don't see the need to use 4-wire binding posts on the resistors, which are the 2-wire variety.

Possibly a dumb question, but should I use a cast metal or a plastic box to house these in? Should I add insulation inside the box or not? I'm thinking about thermal stabilization to ambient temperatures. None of this may matter, as the tempco on these resistors is very low.

tautech:
Have a look at how Joe has set up his ABS DMM check box in later vids in this thread:
https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/

Andreas:
Hello,

the setup from Frank is a possible way to go:

https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg611822/#msg611822

And do not forget the temperature sensor.
The tempco is probably higher than you expect.

With best regards

Andreas

zlymex:
If the resulting standard is not going to be calibrated, the tolerance(of even 0.005%) will contribute to most of the errors when measured by a DMM. In this case, no bother to things like low thermal EMF binding post, box type or thermal stabilization for Z-foils.

If you want the DMM measurement down to, say, 3ppm, you must consider the following factors which roughly has 1 to 3ppm effect each in a normal room:
TCR, Aluminium case, Low EMF binding post(100 Ohm only), aging

quarks:
I always look for good quality parts and prefer/like sealed metal boxes (i.e. from Rose and Raychem) for my projects.

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