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Uncertainties in the SPRT Subranges of ITS-90: Topics for Further Research |
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| Authors: | D. R. White M. Ballico D. del Campo S. Duris E. Filipe A. Ivanova A. Kartal Dogan E. Mendez-Lango C. Meyer F. Pavese A. Peruzzi E. Renaot S. Rudtsch T. Wang K. Yamazawa |
| Affiliation: | 1. Measurement Standards Laboratory of New Zealand (MSL), Lower Hutt, New Zealand 2. National Measurement Institute of Australia (NMIA), Sydney, Australia 3. Centro Espa?ol de Metrologia (CEM), Madrid, Spain 4. Slovak Institute of Metrology (SMU), Bratislava, Slovakia 5. Instituto Português da Qualidad (IPQ), Monte de Caparica, Portugal 6. D.I. Mendeleyev Scientific and Research Institute for Metrology (VNIIM), St Petersburg, Russia 7. TUBITAK Ulusal Metroloji Enstitusu (UME), Gebze-Kocaeli, Turkey 8. Centro Nacional de Metrologia (CENAM), Queretaro, Mexico 9. National Institute of Standards and Technology (NIST), Gaithersburg, MD, USA 10. Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy 11. VSL Dutch Metrology Institute (VSL), Delft, The Netherlands 12. Laboratoire Commun de Métrologie LNE-CNAM (LNE-INM), Paris, France 13. Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany 14. National Institute of Metrology (NIM), Beijing, China 15. National Metrology Institute of Japan (NMIJ), AIST, Tsukuba, Japan |
| Abstract: | The CCT has completed the guide summarizing the uncertainties in the realization of the SPRT subranges of ITS-90 between the triple point of neon (24.5561 K) and the freezing point of silver (961.78 °C). This article identifies aspects of standard platinum resistance thermometry where either data or models are lacking and further research is required. In the calibration of SPRTs, the two main concerns are the need for data on liquidus slopes for the different impurities in the fixed points and improved understanding of the impact of the thermal environment of the fixed point on the realized temperature. In the use of SPRTs, the two largest sources of uncertainty are Types 1 and 3 non-uniqueness and oxidation. The causes of Type 3 non-uniqueness are not yet understood, especially at low temperatures, and there is a paucity of data for the high-temperature subranges. In respect of oxidation, there is a need for validation of the models developed in the 1980s, especially in light of the reduced partial pressure of oxygen used in modern SPRTs. A range of other effects including vacancy effects in SPRTs, isotopic effects in fixed points, and improved statistical methods are discussed. |
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