Research on the Traceability Method of Quantity Value for Vertical Copper Fixed Point Furnace

In the calibration of standard platinum - rhodium 10 - platinum thermocouple standard groups in China, a problem occurs: the vertical copper fixed - point furnace uses the ITS - 90 nominal value but lacks traceability to the high - temperature primary standard, which may cause inaccurate calibration results. This paper devises a calibration scheme with a rotatable - bracket - based device. A photoelectric pyrometer can measure the vertical copper fixed - point furnace vertically and the reference copper fixed - point blackbody horizontally. This comparative method resolves the non - traceability issue and ensures compliance with the high - temperature reference scale. Taking a thermocouple - calibration vertical copper fixed - point furnace as an example, the paper details the calibration device, method, and wall - temperature and emissivity corrections. After comparison and correction, the calibrated temperature is 1084.61 °C, with an uncertainty of 0.09 °C (k = 2). The method resolves the vertical copper fixed - point furnace's traceability problem and offers a new way for the traceability of medium - and low - temperature fixed - point blackbodies below the silver point to the contact temperature primary standard, enabling more accurate calibrations in related fields.