Bilateral comparison of triple point of mercury and melting point of gallium

Project Description

A long sterm SPRT is selected and calibrated at FSB-LPM in Hg-TP, W-TP and Ga-MP. A second set of measurement will be made at MIRS/UL-FE. After its return the SPRT will be recalibrated at FSB-LPM. In the comparison the W will be used.

A final report of the comparison project will be prepared.

Final Report 2012-04-12

The objective of project EURAMET 1127 (Bilateral comparison of triple point of mercury and melting point of gallium) in the field of thermometry was to compare realization of a triple point of mercury (−38.8344 °C) and melting point of gallium (29.7646 °C) between the Slovenian national laboratory MIRS/UL-FE/LMK and the Croatian national laboratory HMI/FSB-LPM using a long-stem 25 Ω standard platinum resistance thermometer (SPRT). MIRS/UL/FE-LMK participated in a number of intercomparisons on the level of EURAMET. On the other hand, the HMI/LPM-FSB laboratory recently acquired new fixed-point cells which had to be evaluated in the process of intercomparisons. A quartz-sheathed SPRT has been selected and calibrated at HMI/LPM-FSB at the triple point of mercury, the melting point of gallium, and the water triple point. A second set of measurements was made at MIRS/UL/FE-LMK. After its return, the SPRT was again recalibrated at HMI/LPM-FSB. In the comparison, the W value of the SPRT has been used. Results of the bilateral intercomparison confirmed that the new gallium cell of the HMI/LPM-FSB has a value that is within uncertainty limits of both laboratories that participated in the exercise, while the mercury cell experienced problems. The difference between measurements made at MIRS/UL-FE/LMK HMI/FSB-LPM was −3.5mK with an uncertainty of the difference of 0.9mK for the triple-point-of-mercury cell and 0.28mK for the melting point of gallium, with an uncertainty of 0.7mK.
After further research, a small leakage in the mercury fixed-point cell has been found.

Results were publishd in International Journal of Thermophysics International Journal of Thermophysics Volume 32, Numbers 7-8, 1544-1552, DOI: 10.1007/s10765-011-1035-6 

Thermometry (T)
Coordinating Institute
MIRS/UL-FE/LMK (Slovenia)
Participating Partners
FSB-LPM (Croatia)