Electronics > Metrology

My first 10kOhm reference resistor

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BU508A:
Hello,

this is my first attempt to build a 10kOhm lab reference resistor to check ordinary DMM.

Bill of material:
- Vishay Y145310K0000V9L from Digikey
- Hirschmann binding post red, 4mm, part number: PKI 10 A AU RT
- Hirschmann binding post black, 4mm, part number: PKI 10 A AU SW
- Silver wire, 1mm diameter, pure silver (999/1000)
- Bopla case, part number Euromas II ET 210
- Solder: Felder "EL", diameter 0.75mm,  Sn96Ag04, part number: 20960720

Further improvements are planned, such as:
- shielding
- put in some sensors for temperature and humidity
- put in some silica gel
- put in something like an USB stick, so I can store calibration data etc. on it
- something else, which I'm not thinking of it right now  ;)

And here are some pictures:

LA7SJA:
How much difference is there between two and four wire measurements of the 10K resistor?

Johan-Fredrik

BU508A:

--- Quote from: LA7SJA on June 09, 2016, 09:13:41 pm ---How much difference is there between two and four wire measurements of the 10K resistor?

--- End quote ---

My 7510 is reading:
- in 4W mode: 10000,000241 Ohms
- in 2W mode: 10000,000259 Ohms

I will do a 24h measure for both modes and post the data here, but not before next week.

Vgkid:

--- Quote from: LA7SJA on June 09, 2016, 09:13:41 pm ---How much difference is there between two and four wire measurements of the 10K resistor?

Johan-Fredrik

--- End quote ---
if you are talking about inside the enclosure, not much if any. Especially is somewhat thick wire is used. In my quest to find out suitable trim resistors. About 6cm of 24awg copper wire yields 2.0mOhms (going from memory). Of course to measure that low a oc ohms meter needs to be used.
   Outside of the enclosure  it does matter.

grumpydoc:
Very nice project.

Are the meters calibrated and if so how long ago (and do you know the actual difference between the reading and resistance standard).

The Vishay .005% resistors do look very nice, especially as they are less than £35 from Farnell.

Just looking at the readings above and assuming the Vishay is within its specified tolerance would give the following observations:

Ignoring the temperature then the Vishay should have a true value of between 9,999.5 and 10,000.5 ohms so the range of possible displays on the Keithley if it is spec is 9999.17 to 10000.83 ohms1 and for the 34401A 9998.69 to 10001.31 ohms2 so your readings are consistent with that.

The max error on the 34401A is .91 of an ohm (10,000.41 - 9999.5) or 91ppm (0.0091%) and on the Keithley it is 0.743 ohms or 74.3ppm - so you can't quite confirm your meters are in spec.

Looking at it the other way, if the Keithley is in spec the true value of the resistor is between 9999.912 and 10000.573 ohms so you are within a hair of knowing the resistor is within its specified tolerance (just 7ppm out on one end of the uncertainty).

1] 30ppm of reading + 3ppm of range on 10k range within 30 days of autocal.
2] 80ppm of reading plus 1ppm of range within 90 days of cal

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