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Determination of the thermodynamic temperature between 236 K and 430 K from speed of sound measurements in helium

2019; IOP Publishing; Volume: 56; Issue: 4 Linguagem: Inglês

10.1088/1681-7575/ab29a2

1681-7575

R. M. Gavioso, D. Madonna Ripa, P. P. M. Steur, R Dematteis, Dario Imbraguglio,

Phase Equilibria and Thermodynamics

Abstract We report speed of sound measurements in helium at 273.16 K and at eight temperatures in the range between 236 K and 430 K. These results determine the difference ( T − T 90 ) between the thermodynamic temperature T and its approximation T 90 by the International Temperature Scale of 1990 (ITS-90). The uncertainty of our measurements of ( T − T 90 ) spans between a minimum of 0.25 mK near 247 K and a maximum of 0.89 mK at the freezing point of indium (429.75 K) with comparable contributions from the uncertainty of our acoustic determination of T and from the uncertainty of our laboratory realization of ITS-90. On the overlapping temperature ranges these results are consistent with other recent acoustic determinations of ( T − T 90 ). We also present evidence that ( T − T 90 ) can be determined with comparably small uncertainties by the alternative, time-saving procedure of measuring the speed-of-sound in helium using only a single, judiciously-chosen, pressure on each isotherm.