The NBS Photoelectric Pyrometer and its Use in realizing the International Practical Temperature Scale above 1063 °C

A photoelectric pyrometer has been developed with which the International Practical Temperature Scale (IPTS) above the gold point, 1063 °C, is realized about 5 times more accurately than with the prevalently used disappearing filament visual pyrometer. Estimated standard deviation uncertainties of realizing the IPTS with the photoelectric instrument are 0.06 deg C at 1063 °C, 0.12 deg C at 1256 °C, 0.27 deg C at 1650 °C, 0.7 deg C at 2330 °C, and 2 deg C at 3525 °C. The design, evaluation, and calibration to realize the IPTS are discussed.