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A multi-partner project is currently being conducted within Working Group 5 (Radiation thermometry) of the CIPM Consultative Committee for Thermometry (CCT), which aims at assigning thermodynamic temperatures to a selected set of high-temperature fixed-points (HTFPs) based on metal-carbon eutectics. A work package of this project (WP2) consists in producing sets of HTFP cells to serve the final phase of the project, assignment of definitive thermodynamic temperatures (WP5). The four fixed-point types are the metal-carbon eutectic points, Re-C (2474 °C), Pt-C (1739 °C), and Co-C (1324 °C), and the Cu point (1084.62 °C). The first phase of the WP2 work treats the construction of HTFP cells, which were carried out by eight National Metrology Institutes (NMIs). The cells were constructed in accordance to instructions laid out in the WP protocol, based on years of experience of WG5 member NMIs. Cells constructed in this way should, in principle, have the required performance in terms of the realized temperature, reproducibility, and long term stability. The constructed cells were then evaluated for their performance in the second phase of the WP. The WP aims at identifying at least four cells of each of the four fixed-point types to be supplied to WP5 of the CCT-WG5 research plan for final thermodynamic temperature assignment. This paper describes the first phase of the WP2. Details of the cell construction conditions and procedures are presented. [ABSTRACT FROM AUTHOR]

Two national metrological institutes of the Russian Federation, VNIIM and VNIIOFI, take part in the international research plan of CCT WG5 for investigation of high-temperature fixed points (HTFP). In the framework of this CCT-WG5 HTFP Research Plan the both institutes have designed and built independently cobalt-carbon (Co-C) eutectic radiation cells. The comparison of the Co-C cells developed by the institutes was carried out with the aim of determination of a difference in the melting temperature due to difference in the constructional characteristics of the cells. The radiance-mode radiation thermometers with central wavelength nearby 650 nm were used for the fixed-point melting temperature measurements. The article presents preliminary results of the comparison, which shows agreement between melting temperature of the compared cells within 20 mK. The details of the comparison are reported. [ABSTRACT FROM AUTHOR]

Tungsten ribbon lamps are the most frequently used means in the temperature range higher than 800 °C for reproduction and precise transfer of a temperature scale by non-contact methods. Lamps have many advantages: a very high reproducibility, stability and durability; use of a lamp over dozens of years with careful and correct operation; and relative simplicity of operation, storage and transportation. The direct correlation of temperature and current through a ribbon enables us to use the advantages of electrical measurements. At the same time lamps have also a number of negative features. Small deviations from the prescribed procedure can lead to unpredictable changes of the performance of a lamp and, even, to irreversible changes of its parameters. The important factor of the quality of transferring the temperature scale is the propinquity of the transferred temperature to the thermodynamic one. Only this factor guarantees the accuracy and unity of temperature measurements of temperature by instruments applying different principles of operation and various designs. However, this is the quality that the lamps do not possess. Their main drawback is selectivity of radiation stipulated by the spectral dependence of emissivity. That is why it is necessary to replace them with blackbodies, which let us rely completely on the definition of the ITS-90. Several years ago at our institute we started investigations on development of special measuring instruments, in which a sensor was located around a miniature blackbody. The aperture of this blackbody could be used as a standard emitter, which temperature was accurately determined by a resistance thermometer. Applying also a standard pyrometer, we refined the reference function of a platinum resistor in the range between the Ag and Cu fixed points. To extend the temperature range up to 1450 °C to 1500 °C we built an instrument in the form of a miniature blackbody made of Pd which was connected to three platinum wires forming Pt-Pd thermocouples. Then we built a similar device made of Pt-Rh alloy. It gave us an opportunity to reach the temperatures up to 1600 to 1700 °C. Having the maximal diameter 8 mm, about 35 mm length and a radiating aperture of diameter 1.8 mm, the device had emissivity about 0.9994, and it was suitable for transfer of the temperature scale, without using conditional temperatures. Its small dimensions allowed for applying it also as a temperature-measuring instrument using the well known and developed contact methods. We discuss in the paper whether such instrument equipped with a simple heater would compete with lamps. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]