This calibration service uses novel fixed points, which for some thermometers can enable calibration with reduced uncertainties at high temperatures. NPL has been extensively involved in researching high temperature fixed points (HTFPs), which are based on the melting temperature of a metal-carbon alloy. These have proven stability and reproducibility, which allows phase transition temperatures to be assigned with very low uncertainty.
We maintain a set of standard HTFPs suitable for use in the calibration of radiation thermometers – listed below with their nominal temperatures. They can be used in combination with pure-metal, ITS-90, fixed points.
These and other alloys (e.g. Palladium, Pd-C (1492 °C), Ruthenium, Ru-C (1954 °C), and Tungsten carbide, WC-C (2748 °C) can be also be supplied with calibration uncertainties (k = 2) are 0.05 % of the temperature (or 1.25 °C at 2500 °C). The calibration is traceable to national standards.
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