Assignment of $$T_{90}$$ T 90 Temperature to a Vertical Co–C Cell for Thermocouple Calibration

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Noble metal thermocouples are often required to be calibrated up to $$1400\,^{\circ }\hbox {C}$$ in fixed points in order to get the lowest uncertainties. The International Temperature Scale of 1990 (ITS-90) defines the temperature of fixed points until the copper point ( $$1084.62\,^{\circ }\hbox {C}$$ ). At higher temperatures, the metal carbon fixed points can be used, and the needed traceability to the ITS-90 is given by means of a standard radiation thermometer. This paper presents the method developed by the Centro Espanol de Metrologia to give traceability to the ITS-90 to the Co–C cell used to calibrate thermocouples by means of a mirror and a standard radiation thermometer with an expanded uncertainty ( $$k =2$$ ) of $$0.5\,^{\circ }\hbox {C}$$ .