At PTB, the unit of temperature is disseminated in about 50 % of all cases by calibrating noble metal thermocouples against fixed points of the International Temperature Scale of 1990 (ITS-90) in the temperature range between 0 °C and 1600 °C. To this end, the phase transitions between the solid and the liquid state (melt) or between the liquid and the solid state (freeze) of pure metals, which occur at well-defined temperatures, are used. In 2016 and 2017, two new fixed-point furnaces for use with fixed-point crucibles filled with the pure metals silver, copper, palladium and platinum were commissioned and metrologically characterized. With the new high-temperature furnace (see figure), it is now possible to use, in particular, the melting temperatures of the noble metals palladium (1553 °C) and platinum (1769 °C). These metals are available in miniature crucibles. This allows the extension of the temperature range for the calibration of special thermocouples to 1769 °C.
Contact:
F. Edler, 7.41, E-Mail: Frank.Edler(at)ptb.de
P. Ederer, 7.41, E-Mail: Petra.Ederer(at)ptb.de