1000 h stability test of the Au/Pd thermocouple at 1000 °C

A newly developed Au/Pd thermocouple has shown very high reproducibility and good immersion characteristics. A stability test of the Au/Pd thermocouple has been conducted for 1000 h at 1000?C in air to assess its suitability for practical application. Two thermocouples from two manufacturers were fabricated and their emf values were checked in a silver freezing-point cell before and after the soaking at 1000 C. It was found that the high-temperature stability of the Au/Pd thermocouple is within ?30mK (2sigma) throughout the test time. This result implies that the Au/Pd thermocouple possesses characteristics which may make it suitable for use as a secondary high-temperature thermometer in industry.