Integrating-sphere-input InGaAs radiometers have been developed at the National Institute of Standards and Technology (NIST) to extend the detector-based calibrations from the Si range to the near-IR. These near-IR radiometers are used to determine the reference spectral irradiance responsivity scale based on the primary standard cryogenic radiometer. The irradiance responsivity scale is then propagated to spectral radiance at the exit port of an integrating sphere. The near-infrared radiation thermometer (NIRT) is calibrated against this detector-based radiance scale. The first phase of this research work is reported here where the relative spectral radiance responsivity of the NIRT has been determined using a monochromator-based system. Thereafter, the relative spectral reponsivity of the NIRT is converted into an absolute responsivity using the signal at the Zn fixed-point blackbody, and then used to extend these calibrations for temperature measurements between 157 degree C and 1000 degree C. The NIRT has also been calibrated in this temperature range against the five fixed points of the ITS-90. The two different calibration approaches for temperature measurements are compared.
Citation: International Journal of Thermophysics
Pub Type: Journals
InGaAs detector, irradiance responsivity, ITS-90, near-infrared, optical radiation, radiance, radiation thermometer, radiance temperature, spectral responsivity, temperature scales