Reference Tables for Platinum 20% Rhodium/Platinum 5% Rhodium Thermocouples

Abstract

Reference tables have been set up for platinum 20% rhodium/platinum 5% rhodium thermocouples over the temperature range 0–1800°C based on measurements made in air with thirteen thermocouples from four wire lots. The thermocouples were calibrated by comparison with standard platinum 10% rhodium/platinum thermocouples from 0 to 1500°C; by freezing point determinations of zinc, antimony, silver, and gold; by melting point determinations of palladium and platinum by the wire method; by comparison with an optical pyrometer from 1200 to 1800°C; and by intercomparisons (with each other) from 0 to 1750°C. The accuracy obtained in the use of the tables is discussed, and data relating to the stability and reproducibility of these thermocouples is presented. Expanded versions of the tables are available as NRC Report No. 7930. A description of a high temperature vacuum furnace is given in the Appendix.