Blackbody-based calibration for temperature calculations in the visible and near-IR spectral ranges using a spectrometer

This paper presents, the results of a method used to create a blackbody-based referenced calibration curve for a spectrometer in the visible and near-IR range. This method would allow the use of optical temperature measurements in high temperature furnaces when distance, environment, and emissivity effects are not accurately known. A probe containing a lens connected to a fiber-optic cable is inserted into a furnace and aimed toward a hot wall source. Spectral intensity data is fed back to a spectrometer and then to a monitoring computer. Initial data is taken along with another method to measure the source temperature, usually a thermocouple or IR-gun. The spectral data is compared to the blackbody intensities generated from the source temperature to create the calibration curve. This calibration curve is then used to correct intensities for temperature calculations using a spectrometer where furnace conditions are similar to those of the calibration data. This calibration method provides much more accurate temperature measurement results than the common practice of using a halogen reference. The results in the visible range compare favorably with those taken in the near-IR range under the same conditions.