Reproduced with
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of Metrologia.

An important note
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ITS-90 Text


  1. Units of Temperature and Introduction from Metrologia 27, 3-10 (1990)
  2. Principles of the International Temperature Scale of 1990 (ITS-90)
  3. Definition of the International Temperature Scale of 1990
  4. Supplementary Information and Differences from Earlier Scales & Appendix

  • List of Tables
  • ITS-90 Tables

    1. Defining Fixed Points of the ITS-90

    2. Effect of pressure on the temperatures of some defining fixed points

    3. Values of the constants for the helium vapour pressure Eq3 (3), and the temperature range for which each equation, identified by its set of constants, is valid.

    4. The constants A0, Ai, Bi, Co, Ci, D0 and Di in the reference functions of equations (9a);(9b);(10a) and (10b) respectively

    5. Deviation functions and calibration points for platinum resistance thermometers in the various ranges in which they define T90

    6. Difference between ITS-90 and EPT-76, and between ITS-90 and IPTS-68 for specified values of T90 and t90


    Summary Table

    A Useful Summary Table; not part of the ITS-90 text.


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