Bilateral Comparison of Aluminum Fixed-Point Cells Using Standard Platinum Resistance Thermometer

Abstract

The objective of Project EURAMET 1114 (Bilateral comparison of a freezing point of aluminum) in the field of thermometry is to compare realization of a freezing point of aluminum (660.323 °C) between the Dutch national laboratory VSL and the Slovenian national laboratory MIRS/UL-FE/LMK using a long-stem 25 Ω standard platinum resistance thermometer (SPRT). Both laboratories had participated in a number of inter-comparisons on the level of EURAMET and also on BIPM CCT level (VSL). MIRS/UL-FE/LMK laboratory recently acquired a new fixed-point cell which had to be validated in the process of intercomparison. A quartz-sheathed SPRT was selected and calibrated at MIRS/UL-FE/LMK at the aluminum freezing point and at the water triple point. A second set of measurements was made on the same SPRT and at the same fixed points at VSL (NL). After its return, the SPRT was again recalibrated at MIRS/UL-FE/LMK. In the comparison the W value of the SPRT was used. The results of the internal and external intercomparisons confirmed that the new aluminum cell of the MIRS/UL/FE-LMK realizes a temperature that agrees with the VSL aluminum fixed point within the uncertainty limits of both laboratories. Furthermore, the results of this bilateral-comparison were compared with results that both laboratories achieved in the EURAMET K4 (Project 820) and were found to be in agreement.