NIST Measurement Services: Radiance Temperature Calibrations
Charles E. Gibson, Benjamin K. Tsai, Albert C. Parr
This document describes the realization and dissemination of the International Temperature Scale of 1990 (ITS-90) above 700 [degrees] C at the National Institute of Standards and Technology (NIST). By using the fundamental principles of blackbody physics, the ITS-90 scale is first fixed at the freezing point of gold (t90 = 1064.18 [degrees] C) and is then extended to temperatures between 700 [degrees] C and 2700 [degrees] C by determining the ratio of the spectral radiance of a tungsten ribbon filament lamp to that of a gold fixed-point blackbody at a wavelength of 655.3 mm. A description of the facilities in the NIST Radiance Temperature Calibration Laboratory is given, along with a discussion of the wavelength calibration, size of source, and linearity issues. The use and calibration of radiance temperature standards are explained. Values of stability and uncertainties in the scale are reported. The expanded uncertainties (k = 2) at 800 [degrees] C and 2300 [degrees] C are 0.6 [degrees] C and 1.4 [degrees] C for ribbon filament lamps, 4 [degrees] C and 7 [degrees] C for disappearing filament optical pyrometers, and 2 [degrees] C and 3 [degrees] C for infrared thermometers.