F. Bourson

Thermodynamic temperature assignment to the point of inflection of the melting curve of high-temperature fixed points.

The thermodynamic temperature of the point of inflection of the melting transition of Re-C, Pt-C and Co-C eutectics has been determined to be 2747.84 ± 0.35 K, 2011.43 ± 0.18 K and 1597.39 ± 0.13 K, respectively, and the thermodynamic temperature of the freezing transition of Cu has been determined to be 1357.80 ± 0.08 K, where the ± symbol represents 95% coverage. These results are the best consensus estimates obtained from measurements made using various spectroradiometric primary thermometry techniques by nine different national metrology institutes. The good agreement between the institutes suggests that spectroradiometric thermometry techniques are sufficiently mature (at least in those institutes) to allow the direct realization of thermodynamic temperature above 1234 K (rather than the use of a temperature scale) and that metal-carbon eutectics can be used as high-temperature fixed points for thermodynamic temperature dissemination. The results directly support the developing mise en pratique for the definition of the kelvin to include direct measurement of thermodynamic temperature.

Dissemination of thermodynamic temperature above the freezing point of silver

The mise-en-pratique for the definition of the kelvin at high temperatures will formally allow dissemination of thermodynamic temperature either directly or mediated through high-temperature fixed points (HTFPs). In this paper, these two distinct dissemination methods are evaluated, namely source-based and detector-based. This was achieved by performing two distinct dissemination trials: one based on HTFPs, the other based on absolutely calibrated radiation thermometers or filter radiometers. These trials involved six national metrology institutes in Europe in the frame of the European Metrology Research Programme joint project ‘Implementing the new kelvin’ (InK). The results have shown that both dissemination routes are possible, with similar standard uncertainties of 1–2 K, over the range 1273–2773 K, showing that, depending on the facilities available in the laboratory, it will soon be possible to disseminate thermodynamic temperatures above 1273 K to users by either of the two methods with uncertainties comparable to the current temperature scale.

A new technique for direct traceability of contact thermometry Co-C eutectic cells to the ITS-90

The eutectic Co-C melting point is a promising system to serve as a thermometric fixed-point in the temperature range above 1084.62 °C (copper freezing point). During the last decade, LNE-Cnam has developed and characterized some fixed-point devices, based on eutectic Co-C alloy, for applications to contact and radiation thermometry. Above 962 °C, the ITS-90 is realized by radiation thermometry by the extrapolation from a Ag, Au or Cu fixed point using the Planck law for radiation. So the only way for assigning a temperature in the scale to a Co-C cell (∼1324 °C) is by radiation thermometry. An indirect method is commonly used to assign a temperature to a high-temperature fixed point (HTFP) cell designed for contact thermometry is to fill a pyrometric cell with the same mixture as the contact thermometry cell. In this case, the temperature assigned to the pyrometric cell is attributed to the contact cell. This paper describes a direct method allowing the determination of the melting temperature realized b...

Comparison of the copper blackbody fixed-point cavities between NIS and LNE-Cnam

This paper describes the results of a bilateral comparison at the copper blackbody fixed point (1084.62 ◦ C), one of the defining fixed points of the International Temperature Scale of 1990 in the high-temperature range. The ‘National Institute of Standards—Egypt (NIS)’ and the ‘Laboratoire Commun de M´ (LNE-Cnam)’ undertook such a comparison using an NIS linear pyrometer ‘LP4’ as a circulating radiation thermometer between the two laboratories. The main objective of this work was to compare the realizations of the copper blackbody fixed point for radiation thermometers and establish the level of agreement between the two laboratories in the high-temperature range. The comparison measurements revealed a slightly lower temperature of the NIS copper point than that of the LNE-Cnam copper point by about 0.08 ◦ C. This difference is not significant with regard to the uncertainty and the stability of the pyrometer estimated as 0.15 ◦ C. A second comparison was made a few months later by comparing simultaneously the two copper points at the LNE-Cnam premises. This comparison allowed determining a temperature difference of 0.045 ± 0.030 ◦ C between the two cells, with the temperature of the LNE-Cnam cell being higher than that of NIS.