Acoustic measurement of the triple point of neon T _Ne and thermodynamic calibration of a transfer standard for accurate cryogenic thermometry

Abstract

We used absolute primary acoustic gas thermometry (AGT) to calibrate a Pt–Co resistance thermometer on the thermodynamic temperature scale by measuring the speed of sound in helium at a temperature T* chosen to be near the temperature of the triple point of neon, T Ne. Prior to the present AGT, the Pt–Co thermometer was used with a neon triple-point cell as part of an interlaboratory comparison. Taken together, the results of the interlaboratory comparison and the present AGT redetermined the thermodynamic temperature T Ne = (24.555 15 ± 0.000 24) K. This new value of T Ne is consistent with other recent determinations obtained with various primary methods. After completing the AGT thermodynamic calibration, we used the Pt–Co thermometer to link T* to the temperature ratios measured by single-pressure refractive-index gas thermometry (SPRIGT) in a different laboratory. (Gao et al 2020 Metrologia 57 065006) Now, the T*-linked SPRIGT system can calibrate other thermometers on the thermodynamic temperature scale T in the range 5 K ⩽ T ⩽ T Ne without using the international temperature scale ITS-90. At most temperatures in this range, the uncertainties of the T*-linked SPRIGT system are smaller than those of the ITS-90 systems used by National Metrology Institutes to calibrate resistance thermometers.

Early Detection of Coal Spontaneous Combustion by Complex Acoustic Waves in a Concealed Fire Source

“…The spontaneous combustion of loose coal creates a solid–gas mixture in which the temperature field and gaseous products change continuously, which makes it difficult to obtain accurate measurements of spontaneously combusted coal. 60 In view of the basic principle of acoustic temperature sensing, the propagation decay rule of acoustic characteristics in the temperature field of spatial and temporal evolution, this paper uses the relevant theories and research in the fields of coal spontaneous combustion theory, acoustic theory, heat transfer and digital signals, etc., in order to develop an outlook on the evolution of combustion sound characteristics in the process of spontaneous combustion for loose coal bodies, the current status of “single source” and “dual source” acoustic temperature sensing technology for hidden fire sources. “Single-source” acoustic thermometry is a method that accepts only one acoustic signal source, the acoustic signal from combustion sound or an external acoustic emission device.…”

Towards Realising the Redefined Kelvin

“…In addition, the realisation of the triple point of Ne at 24.5561 K as well as the lambda transition in superfluid 4 He at 2.1768 K will be investigated as reference points for relative primary thermometry. For the Ne point a new determination of thermodynamic temperature was conducted by acoustic gas thermometry (AGT) [41]. Also, a fast, acoustic gas thermometer ("fast-AGT") is being developed for the range from 4 K to 25 K making feasible the application of AGT in practical primary thermometry.…”

“…These thermometers are being continuously improved to increase their accuracy in the determination of thermodynamic temperature T, and their results and methods are cross checked by mutual comparisons of the differences T -T 90 [63]. Recent such determinations include: the AGT result obtained at LNE-Cnam at 25 K [41] which served as a thermodynamic temperature reference for single-pressure RIGT between 5 K and 25 K at TIPC-CAS [57]; the RIGT results obtained between 14 K and 161 K at NRC and INRiM [49,64] and the DCGT results obtained at PTB between 4 K and 200 K [63,65]. With minor exceptions, the thermodynamic properties which are derived from these experiments show remarkable consistency with the available theoretical estimates.…”

Corrigendum: Measurement of thermodynamic temperature between 5 K and 24.5 K with Single-Pressure Refractive-Index Gas Thermometry (2020 Metrologia 57 065006)

“…2. The value of the reference thermodynamic temperature T * used in an acoustic AGT paper [1] in which the same reference thermometer was employed, the difference being 42 μK at temperatures close to 24.6 K, namely 24.554 948(158) K to 24.554 990(160) K.…”