An International Star Intercomparison of Low-Temperature Fixed Points Using Sealed Triple-Point Cells

Abstract

Bilateral Intercomparison of the ITS-90 Realisations in the Range from −189.3442 °C (Triple Point of Argon) to 961.78 °C (Freezing Point of Silver) between the MIRS/FE-LMK (Slovenia) and the PTB (Germany) AIP Conf.Abstract. An overview of the main results of an international star intercomparison of low-temperature fixed points is given. Between 1997 and 2002, 52 sealed triple-point cells (STPCs) of the thirteen laboratories represented by the authors have been investigated at PTB. The STPCs are used to realise the triple points of hydrogen, neon, oxygen, and argon, respectively, as defining fixed points of the International Temperature Scale of 1990, ITS-90. The melting curves of all STPCs have been measured on the same experimental equipment, adhering strictly to a single measurement program. This protocol enables separation of the effects influencing the melting curves and direct comparison of the thermal behaviour of the STPCs, which are quite different with respect to design, age, gas source, and filling technology. In the paper, emphasis is given to the typical properties of the four fixed-point substances and to the spread of the STPC parameters. Connections between the star intercomparison and completed and on-going international activities, including the CIPM Key Comparisons, are also discussed.

Primary thermometry from 2.5 K to 140 K applying dielectric-constant gas thermometry

“…This extension has no effect on the results for the thermodynamic temperature T, which is deduced from A 1 . In this paper, the high-temperature working equation (equation (25) in [12]) has to be applied only for the determination of κ eff at the TPW.…”

Investigation of low-temperature fixed points by an international star intercomparison of sealed triple-point cells

“…• Parameters of elements for multi-compartment cells [4,8,10,13]. • Universal and special properties of the fixed-point substances [5,8,25,28,29]. • Influence of the freezing and annealing conditions on the thermal recovery, the internal thermal resistance and the equilibrium MCs, especially for neon STPCs [28].…”

“…The measurement protocol has been established in [25] and later on slightly improved, see [4,5,26,27]. To measure an MC applying the calorimetric method, the sample was heated through the solid-to-liquid phase transition under nearly isothermal conditions by the intermittent application of heat.…”

CCT-K2.4: NRC/INTiBS/LNE-Cnam trilateral comparison of capsule-type standard platinum resistance thermometers from 13.8 K to 273.16 K

“…These cells were tested during the EU 'Multicells' project, G6RD-CT-1999-00114 [6]. The triple point of oxygen was realized in the IMGC cell no 202 3-IX-76, which was included in the EUROMET project 377 [7]. The cells were placed in an adiabatic cryostat as described in [8].…”

“…To realize the mercury and water triple points, cell Hg 220 and H 2 O cell B11/50/465 were used with their respective baths manufactured by ISOTECH. Both of these cells are being tested in bilateral comparisons under the EUROMET projects 895 6 and 914 7 .…”