Metal-Carbon Eutectics to Extend the Use of the Fixed-Point Technique in Precision IR Thermometry

摘要

The high-temperature extension of the fixed-point technique for primary calibration of precision infrared (IR) thermometers was investigated both through mathematical simulations and laboratory investigations. Simulations were performed with Go-C (1,324℃) and Pd-C (1, 492℃) eutectic fixed points, and a precision IR thermometer was calibrated from the In point (156.5985℃) up to the Co-C point. Mathematical simulations suggested the possibility of directly deriving the transition temperature of the Co-C and Pd-C points by extrapolating the calibration derived from fixed-point measurements from In to the Cu point. Both temperatures, as a result of the low uncertainty associated with the In-Cu calibration and the high number of fixed points involved in the calibration process, can be derived with an uncertainty of 0.11℃ for Co-C and 0.18℃ for Pd-C. A transition temperature of 1,324.3℃ for Co-C was determined from the experimental verification, a value higher than, but compatible with, the one proposed by the thermometry community for inclusion as a secondary reference point for ITS-90 dissemination, i.e., 1,324.0℃.