Calibration of high-temperature Fourier transform infrared spectrometer data with low-temperature calibration measurements.

Abstract

Fourier-transform (FT) spectrometer data must be calibrated using at least two reference sources to yield a target temperature. An experiment was performed with an ABB MR304 FTIR spectrometer to determine the best calibration method for data from its MCT (mercury-cadmium-telluride) and InSb (indium-antimonide) detectors at temperatures well above the reference temperatures (extrapolation), as well as to analyze the effects of mesh screens on the detector behavior and calibration quality. Four datasets were collected and plotted on radiance versus instrument response plots to analyze the detector behaviors and to test how well lower temperature points predicted higher temperature points with linear and quadratic fitting. It was determined that the MCT detector is quadratic for low wavenumbers at a low signal but otherwise linear, and that the InSb detector is linear for all wavenumbers. It was concluded that (1) mesh screens have a detrimental effect on calibration quality and (2) linear calibration is the better method for calibration, including extrapolation.