The triple point of water serves to define the kelvin, the unit of thermodynamic temperature, in the International System of Units (SI). Furthermore, it is the most important fixed point of the International Temperature Scale of 1990 (ITS-90). Any uncertainty in the realization of the triple point of water contributes directly to the measurement uncertainty over the wide temperature range from 13.8033 K to 1234.93 K.The Consultative Committee for Thermometry (CCT) decided at its 21st meeting in 2001 to carry out a comparison of water triple point cells and charged the BIPM with its organization.Water triple point cells from 20 national metrology institutes were carried to the BIPM and were compared with highest accuracy with two reference cells. The small day-to-day changes of the reference cells were determined by a least-squares technique. Prior to the measurements at the BIPM, the transfer cells were compared with the corresponding national references and therefore also allow comparison of the national references of the water triple point.This report presents the results of this comparison and gives detailed information about the measurements made at the BIPM and in the participating laboratories. It was found that the transfer cells show a standard deviation of 50 µK; the difference between the extremes is 160 µK. The same spread is observed between the national references.The most important result of this work is that a correlation between the isotopic composition of the cell water and the triple point temperature was observed. To reduce the spread between different realizations, it is therefore proposed that the definition of the kelvin should refer to water of a specified isotopic composition.The CCT recommended to the International Committee of Weights and Measures (CIPM) to clarify the definition of the kelvin in the SI brochure by explicitly referring to water with the isotopic composition of Vienna Standard Mean Ocean Water (VSMOW). The CIPM accepted this recommendation and the next edition of the SI brochure will include this specification.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).
The current state of the art for temperature realization and dissemination above 1300 K is through the MeP-K-19 [1]. A limited set of high-temperature fixed points (HTFPs), an essential component of the MeP-K-19, has their temperature determined (Co–C (1597 K), Pt–C (1011 K) and Re–C (2747 K)). It is really a need to increase the HTFPs available for realization and dissemination of the high-temperature MeP-K. Fe–C (1426 K) and Pd–C (1765 K) has been less investigated, their thermodynamic temperature hasn’t been definitively determined, and they have been considered good candidates for their inclusion in the MeP-K in the EMPIR project “Real-K” [2]. This paper describes the construction, characterization, and measurement of HTFPs of Fe–C and Pd–C at Centro Español de Metrología as part of its contribution to the EMPIR project “Real-K”. Cells made have hybrid-type crucibles and they have been filled applying the piston method. A series of 6 HTFPs has been constructed: 3 Fe–C and 3 Pd–C. Points of inflection of the melting plateaux are repeatable after several initial measurement cycles. Their corresponding International Temperature Scale (ITS-90) temperatures (t90), referenced to a Cu fixed point, and thermodynamic temperatures (t), by means of the spectral responsivity calibration, have been calculated. Additionally, the influence of the furnace in the temperature assigned to the cells has been determined for different furnaces types (one zone and three zone) and different temperature profiles.
The National Metrology Institute of Spain (CEM) has designed, characterized, and set-up its new system to calibrate thermocouples and infrared radiation thermometers up to 1600 • C by comparison to radiation thermometry. This system is based on a MoSi 2 three-zone furnace with a graphite blackbody comparator. Two interchangeable alumina tubes with different structures are used for thermocouples and radiation thermometer calibrations. The reference temperature of the calibration is determined by a standard radiation thermometer. Normally, this is used at CEM to disseminate the International Temperature Scale of 1990 (ITS-90) in the radiation range, and it refers to the Cu fixed point. Several noble metal thermocouples and infrared radiation thermometers with a central wavelength near 900 nm have been calibrated, and their uncertainty budgets have been obtained.
Abstract. Nowadays, determining the temperature of flames is a challenging measurement in industry. The EMPIR project 14IND04 EMPRESS, in its WP4, address these temperature measurements. The Infrared Lab at the Physics Department of Universidad Carlos III of Madrid (UC3M) has developed a technique for measuring the temperature of a standard flame, in collaboration with the Centro Español de Metrología (CEM). An Imaging Fourier Transform Spectrometer (FTIR) has been used to acquire the emitted radiation coming from the flame and establish its temperature through several processing stages. This equipment has been calibrated with standard radiation thermometers and blackbodies at CEM.
A bilateral comparison between Centro Español de Metrología (CEM), Spain, and Laboratorio Costarricense de Metrología (LACOMET), Costa Rica, in the range 83.8058 K to 993.473 K has been developed during 2009 aimed at providing linkage of LACOMET results to those of the CCT key comparisons CCT-K3 and CCT-K4. The participation of CEM in the EURAMET regional key comparisons EUROMET.T-K3 and EUROMET.T-K4 is the basis of the link.This report presents the results of this comparison, provides detailed information of the measurements performed by the participating laboratories, and links the comparison results to the CCT and EURAMET related comparisons.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
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