Relative Pressure Dependence of Chromel/Alumel and Platinum/Platinum− 10% Rhodium Thermocouples

Abstract
Measurement made under hydrostatic conditions to 7 kbar of the relative thermal emf's of chromel/alumel and platinum/platinum−10% rhodium thermocouples indicates a pressure correction for platinum couples of 0.57 ± 0.03°C/kbar from about 600 to 1000°C. Chromel/alumel couples are found to be pressure dependent above about 720°C and to degrade rapidly at temperatures above 800°C. Systematic differences of unknown origin are found between pressure corrections measured with increasing and decreasing pressure.