Realization of Open Copper Fixed-Point Cells for Thermocouple Calibration.

BNM-LNE had studied Pt/Pd thermocouple behavior with the aim of adopting this type of sensor as an approximation of the ITS-90 above 660 °C. In order to complete a set of fixed-point cells which are available for the calibration of Pt/Pd thermocouples and other Pt-based thermocouples, BNM-LNE has recently developed an open copper fixed-point cell. This cell was developed as a test cell in order to improve the realization method, to estimate uncertainty contributions and also to determine the freezing temperature traceable to ITS-90. The cell was checked using a copper fixed-point mini-cell. This paper describes all the steps of the construction needed for cell realization and its characterization. The choice to manufacture an open cell at this point is justified in the paper. Metal impurities, metal filling conditions in the cell and atmospheric pressure effects are studied. The freezing temperature of ITS-90 was preliminarily estimated by contact thermometry awaiting a comparison with a radiation thermometry realization. The consistency of this estimated uncertainty will be confirmed by a comparison with other NMI facilities organized in Europe (Euromet project 624). This comparison is under process. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]