Comparison of low-ohmic resistors (100 mohm, 1 mohm, 10 mohm and 100 mohm)

Project Description

This project was initiated by work at NMi VSL aimed at replacing an old set-up for low-ohmic measurements (based on a GL9920 current comparator) with a new, automated, set-up based on a MI6011A range extender with built in current comparator and external nV-meter. The evaluation of the old and new setup showed that the results agreed within their respective uncertainties. Still, a need was felt for an independent verification of the new set-up via a comparison.
It appears that very few comparisons on low-ohmic resistors have been organized. So the second purpose of this project is to see at what level resistance comparisons of low-ohmic resistance values can be performed. An important aspect here is the power dissipation used in the measurements, where an optimum has to be found between heating effects and signal strength. In the present comparison, for each resistor the measurements will be performed at three different dissipation levels.

This comparison will be organized following the guidelines for comparisons suggested by the BIPM. A technical protocol is formulated before the start of the comparison.
The proposed time schedule is February – September 2005.
If there is an interest of other laboratories in joining this comparison, NMi and NPL propose to first finish this project. The present project may then be regarded as a trial round for a subsequent, larger, comparison.

Final Report 2008-10-18

The project has been completed and the report can be downloaded here>>