– the intergovernmental organization through which Member States act together
     on matters related to measurement science and measurement standards.
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Resolution 9 of the 21st CGPM (1999)
Version française
Extension of the International Temperature Scale below 0.65 K

    The 21st Conférence Générale des Poids et Mesures,

    considering that

  • many important research activities are in progress at temperatures below 0.65 K,
  • these researches require an accepted temperature scale which closely represents thermodynamic temperatures,
  • the direct measurement of thermodynamic temperature is often difficult and time-consuming at temperatures below 0.65 K down to a few millikelvin, but at temperatures much lower than this direct measurements once again become feasible,
  • considerable work has already been accomplished towards the development of a temperature scale for the range from 0.65 K down to 1 mK based on the melting pressure of 3He,
  • invites the International Committee to prepare a 3He melting pressure equation as a function of thermodynamic temperature to serve as the basis for an extension of the ITS-90 below its present lower limit of 0.65 K.

Comptes Rendus de la 21e CGPM (1999), 2001, p.332
Metrologia, 2000, 37(1), 87-98

The reader should note that the official version of this Resolution is the French text.

Other Resolutions of the 21st CGPM (1999)
Resolution 1
Resolution 2
Resolution 3
Resolution 4
Resolution 5
Resolution 6
Resolution 7
Resolution 8
Resolution 9
Resolution 10
Resolution 11
Resolution 12
Resolution 13