Summary of achievements of the European Metrology Research Programme Project ‘‘Implementing the new Kelvin” (InK 1)

partially_open5sìWe report a summary of the technical achievements of the European Metrology Research Programme Project (EMRP) ‘‘Implementing the new Kelvin” (InK 1). In short these are: The first determination of definitive thermodynamic temperatures for the point of inflection of the high temperature fixed points of Re-C, Pt-C and Co-C as well as a new evaluation of the Cu freezing point. The first trial of the new dissemination mechanisms for thermodynamic temperature at high temperatures, as described in the mise en pratique for the definition of the kelvin (MeP-K). A new ultra-low uncertainty thermodynamic evaluation of T T90 from about 30 K to 303 K, with particular emphasis on temperatures around the water triple point (273.16 K). The first re-evaluation of T T2000 from 0.02 K to about 1 K with an uncertainty of <1%. Taken together these results represent a significant advance in primary thermometry. We also give a brief introduction to the successor project (InK 2) and discuss the impact of this work on the kelvin redefinition and next version of the MeP-K (i.e. the MeP-K-19)openMachin, G.; Engert, J.; Gavioso, R.; Sadli, M.; Woolliams, E.Machin, G.; Engert, J.; Gavioso, ROBERTO MARIA; Sadli, M.; Woolliams, E

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

Velocità del suono nei fluidi Speed of sound in fluids

La velocità del suono è una grandezza fisica determinata dalle proprietà – temperatura, pressione, composizione – e dallo stato di aggregazione del mezzo in cui la perturbazione acustica si propaga. La sua misura sperimentale permette quindi di ottenere una stima delle proprietà che caratterizzano tali stati in una varietà di condizioni e di scale dimensionali, da microscopiche a planetarie. Limitandosi al caso di mezzi fluidi omogenei, si descrivono una serie di applicazioni della misura della velocità del suono che hanno un interesse scientifico o pratico attuale. Per ognuna di esse la descrizione è accompagnata da una illustrazione essenziale dei principi teorici che ne costituiscono il fondamento.The speed of sound is a physical quantity determined by the properties – temperature, pressure, composition – and by the state of matter of the acoustic propagation medium. As a consequence, the experimental determination of the speed of sound may provide an estimate of these properties in a variety of physical conditions over a range of dimensional scales spanning from microscopic to planetary. Limiting the discussion to consider the case of homogenous fluids, a number of current applications of such measurements which have a scientific or practical interest is reviewed. The description of each application is supplemented by a succinct illustration of the underlying theoretical basis