Comparison of realisations of aluminum and silver freezing-point temperatures

Project Description

The agreed project will compare the realization of Al (660.323 °C) and Ag (961.78 °C) fixed-points at SMS/SPI with the realizations of Al and Ag fixed-points at PTB. The intercomparisons will be piloted by PTB.

The pilot laboratory will calibrate one SPRT at the Al fixed-point and one HTSPRT at the Al and Ag fixed-points. The resistances of the thermometers at the triple point of water are around 25 Ω for SPRT and around 0.6 Ω> for HTSPRT. The calibrated thermometers will be hand carried to SMS/SPI, where the thermometers will be calibrated at Al and Ag fixed-points of SMS/SPI. The calibration report should include at least three W-values of the SPRT at Al fixed point, three W-values of the HTSPRT at Al fixed point and three W-values of the same HTSPRT at Ag fixed point, together with the associated uncertainties. The thermometers will be returned to PTB after the calibration at SMS/SPI.

Final Report 2005-03-30

The project has been finished and the reults can be downloaded here>>.

The conclusion was that:
"For two adjacent measurements in all cases an agreement within the combined uncertainty was found. Unfortunately the HTSPRT was found to be unstable: The first and final measurements at PTB do not agree within the uncertainties. Therefore this intercomparison is only of limited value for evaluation of the CMC values."It can be concluded from the results that EUROMET T-K4 must be organised in such a way that there is some redundancy in the measurements."