Comparison of fixed point cells (TP of Hg, MP of Ga, FP of Sn, FP of Zn, FP of Al, FP of Ag) and comparison of the W at the argon point

Project Description

This project is part of bilateral project between Slovenia and Germany. The proposed project will compare realisation of the fixed points at SMIS/FE-LMK with realisation of the fixed points at PTB. The fixed points compared in scope of this project are the triple point of mercury, the melting point of gallium, the freezing point of tin and freezing point of zinc. Furthermore, the comparison of W at triple point of argon will be made.

In the first phase of the proposed project, the fixed points cells will be compared at the PTB. For the comparison of the cells we will use one thermometer from SMIS/FE-LMK and at least one from the PTB.

In the second phase of the proposed project one standard platinum resistance thermometer from the PTB will be calibrated at fixed points in Slovenia. Additionally, W at the triple point of argon will be measured for later comparison.

With this two phase comparison we will be able to compare fixed point cells as well as procedures in the laboratories.


Final Report 2005-03-31

The intercomparison was performed in three stages.

During the first stage of the intercomparison, SMIS/FE-LMK cells were compared against the PTB cells using well defined baths and furnaces. During the process of intercomparison, several different long stem platinum thermometers were used, including the SMIS/FE-LMK Tinsley 274720. The measurements were performed in the period from 21.02.2000 to 03.03.2000.

All resistance measurements were performed with the automatic ASL F18 alternating current bridge in combination with the 10 ohm or the 25 ohm resistor, depending on the resistance of the standard platinum thermometer. The measurements were performed with a current of 1 mA. For the determination of the self heating correction, additional measurements with a current of 2 mA were made. The hydrostatic head corrections were made in accordance with dimensions of the cells. In the Table 1, one can see measured differences, thermometers used for those measurements and the total uncertainty. The uncertainty budget is presented in the Table 2.

In the second stage of the intercomparison, the PTB brought to SMIS/FE-LMK laboratory their reference platinum resistance thermometer, CHINO RS 921-7, which was calibrated in the range from the triple point of mercury up to the freezing point of zinc. Additionally, since it is very hard to transport the argon triple point with accompanying apparatus, the value at the triple point of argon was measured. After the return of the thermometer to the PTB, this measurement was repeated in the PTB reference argon point. The measurements were performed in the period from 09.10.2000 to 23.10.2000.

All resistance measurements were performed with the automatic MI 6010 B direct current bridge, with 10 seconds current alternation period in combination with the >25 ohm resistor. The measurements were performed with a current of 1 mA. For the determination of the self heating correction, additional measurements with a current of 2 mA were made.

As a monitoring thermometer at different fixed points, combination of previously calibrated Tinsley thermometers and Rosemount thermometers were used.

In the third stage of the intercomparison, SMIS/FE-LMK cells (aluminium and silver) were compared against the PTB cells using well defined baths and furnaces. During the process of intercomparison, several different long stem platinum thermometers were used

Results were presented at 8th Temperature Symposium in Chicago 2002 (see attached paper)

Subjects
Thermometry (T)
Coordinating Institute
MIRS/UL-FE/LMK (Slovenia)
Participating Partners
PTB (Germany)