High temperatures: new fixed points and thermodynamic temperature

  1. French College of Metrology
  1. M. Sadli,
  2. B. Rougié,
  3. F. Bourson and
  4. S. Briaudeau

Published Online: 3 FEB 2010

DOI: 10.1002/9780470611371.ch10

Transverse Disciplines in Metrology

Transverse Disciplines in Metrology

How to Cite

French College of Metrology (2009) High temperatures: new fixed points and thermodynamic temperature, in Transverse Disciplines in Metrology, ISTE, London, UK. doi: 10.1002/9780470611371.ch10

Author Information

  1. Conservatoire National de Arts et Métiers, Institut National de Métrologie LNE-INM/Cnam, 61, rue du Landy 93210 La Plaine Saint-Denis, France

Publication History

  1. Published Online: 3 FEB 2010
  2. Published Print: 1 JAN 2009

ISBN Information

Print ISBN: 9781848210486

Online ISBN: 9780470611371



  • ageing;
  • reproducibility;
  • robustness;
  • thermal optimization;
  • radiometric method


ITS-90 temperature measurements above the copper point are performed by extrapolating the spectral radiance from a fixed point (Ag 961.78°C, Au 1064.18°C or Cu 1084.62°C) using the Planck law for radiation. This extrapolation will mathematically induce an increase of the uncertainty and will also be affected by the base parameters of the extrapolating instrument: the pyrometer.

To help avoid this inconvenience in a future temperature scale or a different manner for putting the kelvin into practice, our institute has worked for several years now on two parallel paths: the thermodynamic temperature measurement with a direct traceability to the cryogenic radiometer, and the study of high-temperature fixed points based on metal(carbide)-carbon eutectics. These two paths are coming today to a crossroads where we should contribute to the international effort aiming to assign thermodynamic temperatures to a set of high-temperature fixed points by 2011–2012 [1] toward a new international temperature scale.

In this paper, we will review the up-to-date progress of our work in the field of high temperature fixed points, thermal optimization of the furnace used for implementing these fixed points and the new means devoted to thermodynamic temperature measurement in our institute.