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

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

A determination of the molar gas constant R by acoustic thermometry in helium

We have determined the acoustic and microwave frequencies of a misaligned spherical resonator maintained near the temperature of the triple point of water and filled with helium with carefully characterized molar mass M = (4.002 6032 ± 0.000 0015) g mol-1, with a relative standard uncertainty ur(M) = 0.37×10-6. From these data and traceable thermometry we estimate the speed of sound in our sample of helium at TTPW = 273.16 K and zero pressure to be u0 2 = (945 710.45 ± 0.85) m2 s-2 and correspondingly deduce the value R = (8.314 4743 ± 0.000 0088) J mol-1 K-1 for the molar gas constant. We estimate the value k = R/NA = (1.380 6508 ± 0.000 0015) × 10-23 J K-1 for the Boltzmann constant using the currently accepted value of the Avogadro constant NA. These estimates of R and k, with a relative standard uncertainty of 1.06 × 10-6, are 1.47 parts in 106 above the values recommended by CODATA in 2010

Quantum-based realizations of the pascal: status and progress of the EMPIR-project: quantumpascal

The QuantumPascal (QP) project combines the capabilities of 12 European institutions to enable traceable pressure measurements utilizing quantum-based methods that evaluate the number density instead of force per area to target the wide pressure range between 1 Pa and 3 MPa. This article summarizes the goals and results since the project start in June 201

The IMERAPlus Joint Research Project For Determinations Of The Boltzmann Constant

Abstract. To provide new determinations of the Boltzmann constant, k, which has been asked for by the International Committee for Weights and Measures concerning preparative steps towards new definitions of the kilogram, the ampere, the kelvin and the mole, an iMERAPlus joint research project has coordinated the European activities in this field. In this major European research project the Boltzmann constant has been determined by various methods to support the new definition of the kelvin. The final results of the project are reviewed in this paper. Determinations of the Boltzmann constant k were achieved within the project by all three envisaged methods: acoustic gas thermometry, Doppler broadening technique, and dielectric constant gas thermometry. The results were exploited by the interdisciplinary Committee on Data for Science and Technology (CODATA) in their 2010 adjustment of recommended values for fundamental constants. As a result, the CODATA group recommended a value for k with a relative standard uncertainty about a factor of two smaller than the previous u(k)/k of 1.7×10 −6

The Euramet Metrology Research Programme Project Implementing the New Kelvin (InK)

The kelvin, along with the ampere, kilogram, and the mole are likely to be redefined in terms of fundamental constants, in line with Conférence Générale des Poids et Mesures resolution 1 (2011), sometime before 2020. In advance of, and to support, the redefinition, a mise en pratique of the definition of the kelvin (MeP-K) is currently being prepared. The Euramet Metrology Research Programme Implementing the newkelvin (InK) project will coordinate research activity in this field with the objective of improving primary thermometry over the range from 0.0009K to >3000K. Specifically, the project will aim to pursue the following three broad objectives: (1) Support the development of primary thermometry techniques for the realization and dissemination of thermodynamic temperatures, particularly at high (>1300K) and low (<1K) temperatures. This is a major objective of InK because primary thermometry methods at the extremes of temperature should, in principle, have lower uncertainties than defined scales. (2) Determine low uncertainty values of T − T90 in the temperature region where the defined scale is expected to continue providing the lowest uncertainties. This will support the development of theMeP-K and help in the construction of a reliable data set for any possible future temperature scale. (3) Use different thermodynamic thermometry methods to re-determine T − T2000 and therefore hopefully understand the cause of the discrepancy in the background data that constitutes the Provisional Low Temperature Scale of 2000 (PLTS-2000). An overview of the InK project, activities, and intended outcomes is given in this paper

Velocità del suono e proprietà termodinamiche dei gas

La velocità del suono u nei fluidi puri e nelle miscele è una grandezza fisica intrinsicamente legata alle variabili termodinamiche del fluido stesso, nel senso che, se sono note le proprietà termodinamiche, è possibile calcolare u e viceversa la misura di precisione di u consente di determinare alcune fondamentali proprietà termodinamiche del fluido. In questa memoria vengono brevemente passate in rassegna le più importanti applicazioni legate alla misura di precisione della velocità del suono e illustrate le caratteristiche e le prestazioni di un apparato sperimentale dedicato a questa applicazione di metrologia acustic