PROPOSALS FOR THE NEW DEFINITION OF THE KELVIN
Journal Title: Metrology and Measurement Systems - Year 2008, Vol 15, Issue 2
Abstract
The International Committee forWeights and Measures (CIPM) has had a long-term aim of defining all of the base units in the terms of fundamental physical constants to eliminate any artifact on material dependencies. In 2005, in Recommendation 1, the CIPM approved preparative steps towards new definitions of the kilogram, the ampere, the Kelvin and the mole in terms of fundamental constants [1, 2]. The unit of temperature, the Kelvin, can be defined in terms of the SI unit of energy, the joule, by fixing the value of the Boltzmann constant k which is simply the proportionality constant between temperature T and thermal energy kT [3]. The new definition would be in line with modern science where nature is characterized by statistical thermodynamics, which implies the equivalence of energy and temperature as expressed by the Maxwell-Boltzmann equation. The Boltzmann constant k is not connected with the other fundamental constants, there are no alternatives to the linking of the Kelvin aside from the exact value of the constant k. In practice, no universal instrument for measuring energy exists while energy appears in different forms, e.g. temperature. Currently, several experiments are underway to determine k using primary thermometers of different types [3, 4]. From the point of view of practical thermometry it is necessary to determine what uncertainty in the measured value of k is needed to apply it as the temperature unit. It would be of the order in the present realization of the triple point of water: = 1.8×10-7. At present its uncertainty is about one order of magnitude higher.
Authors and Affiliations
LESZEK LIPIŃSKI, ANNA SZMYRKA-GRZEBYK
Keywords
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