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NIST ITS-90 Thermocouple Database


NIST reference functions and tables of thermocouple electromotive force (emf) versus temperature have been adopted as standards by the American Society for Testing and Materials (ASTM) [1] and the International Electrotechnical Commission (IEC) [2]. All letter-designated thermocouple types are manufactured to match these standards to within specified tolerances. Furthermore, calibrations of individual thermocouples are often expressed in terms of the deviation in emf of the test thermocouple from the emf value given by the reference function. This database reproduces a subset of the tables and reference functions of NIST Monograph 175, "Temperature Electromotive Force Reference Functions and Tables for the Letter-Designated Thermocouple Types Based on the ITS-90" [3], by G. W. Burns, M. G. Kaeser (formerly Scroger), G. F. Strouse, M. C. Croarkin, and W. F. Guthrie. All temperatures used by this database are given on the International Temperature Scale of 1990 (ITS-90) [4], and all emf values are given in units of the 1990 SI volt [5]. Details of the ITS-90 are given in Appendix A .