Author Topic: Homemade resistance standard  (Read 6047 times)

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Offline mojoe

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Homemade resistance standard
« on: March 07, 2016, 06:17:09 pm »
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.
 

Online tautech

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Re: Homemade resistance standard
« Reply #1 on: March 07, 2016, 06:25:17 pm »
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/
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Can help with advice on Siglent equipment when time allows.
 

Offline Andreas

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Re: Homemade resistance standard
« Reply #2 on: March 07, 2016, 08:01:24 pm »
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
 

Offline zlymex

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Re: Homemade resistance standard
« Reply #3 on: March 08, 2016, 04:53:28 am »
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
 

Offline quarks

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Re: Homemade resistance standard
« Reply #4 on: March 08, 2016, 05:13:49 am »
I always look for good quality parts and prefer/like sealed metal boxes (i.e. from Rose and Raychem) for my projects.
« Last Edit: March 08, 2016, 05:40:32 am by quarks »
 

Offline plesa

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Re: Homemade resistance standard
« Reply #5 on: March 08, 2016, 09:31:50 pm »
Rolec AlPlus AP100 which is used be Wekomm
http://www.rolec.de/en/Enclosures-Accessories/aluPLUS.htm
is my favourite.
 

Offline branadic

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Re: Homemade resistance standard
« Reply #6 on: March 09, 2016, 07:55:39 pm »
I recommend a die-cast aluminum box too and fill it with an oil bath or similar. In "Long term characterization of voltage references" they used "...a bath of perfluoropolyther heat transfer fluid (Galden HT 110) which has a high resistance (about 10e15  ? · cm) and a low viscosity (hence a good temperature homogeneity). This configuration also prevents any influence of the hygrometry and reduces the thermo-electric voltages at the soldered junctions on the electronics boards...".
Computers exist to solve problems that we wouldn't have without them. AI exists to answer questions, we wouldn't ask without it.
 

Offline babysitter

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Re: Homemade resistance standard
« Reply #7 on: March 09, 2016, 08:07:21 pm »
My coworker changed from Novec to a Flourinert product at work, maybe I should steal that leftover bottle. :)
I'm not a feature, I'm a bug! ARC DG3HDA
 

Offline Chipguy

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Re: Homemade resistance standard
« Reply #8 on: March 16, 2016, 06:42:36 am »
How useful would it be to have a fully programmable resistance decade that can be used as a resistance standard?
It won't be as precise as a Wekomm resistor but perform as good as a 5.5 digit multimeter's specs can measure them.
In order to calibrate and adjust it, it's necessary to use a 8.5 digit multimeter.
Planned range: 1 Ohm to 100K, resolution: 5 digits

Possible Applications:
Plain adjustable R decade of course
RTD simulation (down to 0.02°C precision PT100)
Simulation of fluid conductivity in water
Precision voltage source (together with a precision current source)
etc.
Where is that smoke coming from?
 


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