Thermocouple calibrations currently require investigation of physical and chemical properties of each instrument, as thermocouple accuracy depends on the uniformity of these properties along the length of each thermo-element. Uniformity tends to degrade in use, also affecting thermocouple performance. Insufficient knowledge of these processes has hampered development of a standard method for measuring such ‘inhomogeneity’, and there’s no standard traceable measurement method to verify performance in-situ.
The project will develop practical methods and devices traceable to the International Temperature Scale of 1990 (such as dual-type thermometers and heater arrays) to enable thermocouple drift to be checked in-situ. To determine thermocouple inhomogeneity, an easy-to-use thermocouple will be developed integrating miniature fixed-point cells (a technology that realises liquid-solid equilibrium temperatures of high-purity metal elements without reference thermometers). The outcome will be at least a doubling of the certainty of temperature measurement using thermocouples in the range 232 °C to 1100 °C, resulting in increased efficiency of industrial processes that require precise temperature measurement.