EMF changes of Pt/Pd thermocouples at the Cu freezing point

The drift in EMF of Pt/Pd thermocouples during successive calibrations at the Cu freezing point was measured. The different heat treatment was performed to each thermocouple before the calibration. The magnitude of the drift of the thermocouples depended on the heat treatment. The heat treatment at 850/spl deg/C or 1030/spl deg/C for 100 hours resulted in reduction of the drift.