Highly accurate temperature measurements with pure element thermocouples

摘要

Thermocouples made from pure elements, such as gold versus platinum or platinum versus palladium, do not exhibit the oxidation effects that limit the performance of platinum-rhodium alloy thermocouples. Consequently, the stability and homogeneity of pure element thermocouples far exceed those of the best alloy thermocouples. Examples of the fabrication, calibration, and performance of Au/Pt and Pt/Pd thermocouples are discussed. Recent studies of Pt/Pd thermocouples have focused on thermoelectric stability, the effects of oxidation, and the determination of a temperature-emf reference function for temperatures up to 1500°C. Pure element thermocouples are especially appropriate for use as secondary reference thermometers at high temperatures or for measuring temperature profiles of furnaces for critical processes.