Derivation of the CCT-68 Reference Function of the International Practical Temperature Scale of 1968

Abstract

Between 13.81 K and 273.15 K, standard platinum resistance thermometer calibrations on the IPTS-68 are referred to the CCT-68 W versus T reference function, which is designed to simulate as closely as possible the behaviour of a typical high-quality resistance thermometer. In choosing the function the authors took account of: a number of thermodynamic temperature measurements in various laboratories; an intercomparison of several of these scales; and certain requirements for internal consistency in the function. These considerations were to some extent conflicting, and an element of judgment was required in effecting a compromise between them.