Resolution 9 of the 21st CGPM (1999)

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.

DOI : 10.59161/CGPM1999RES9E

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

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