The foundations of thermometry

The whole field of fundamental thermometry in the range 0.5 to about 3000K is reviewed. A historical outline of the development of the theory and methods of thermometry is given. It is shown how the need arose for practical temperature scales and eventually for an international organization responsible for drafting and promulgating an International Practical Temperature Scale. The areas that combine to produce practical scales of temperature are described. These are thermodynamic temperature measurement, the realization of fixed points, precision interpolating instruments, and radiation thermometry. Detailed discussions are included of many of the experimental and theoretical problems at present encountered in precision work. All of this is brought together in a discussion of the present IPTS-68, including an assessment of its merits and defects and a look towards future developments.