Step change improvements in high-temperature thermocouple thermometry

Thermocouples are the most widely used and most widely misunderstood temperature sensor in industry. This paper will begin with an introduction to thermocouples, how they work and the different types of thermocouple. The commonest and most misunderstood source of uncertainty, thermoelectric homogeneity, will be described. The paper will then discuss the concept of measurement traceability and new calibration methods that can give <1 °C uncertainty up to 1500 °C. The paper will conclude by describing some thermocouple innovations; a) industrial versions of pure thermoelement types (Pt/Pd) and b) self-validating “smart-sensors” which enable thermocouples to remain in calibration even when operating at extreme temperatures e.g. tungsten rhenium (W-Re) refractory metal types (e.g. type C) above 2200 °C.