Spectroscopic slope temperature measurements using a noncalibrated tungsten lamp as a reference light source

The spectroscopic slope method for temperature measurements requires the calibration of the spectrometer spectral response, unless the spectral lines or band components all occur in such a small wavelength interval that the response is constant. A calibrated tungsten lamp is generally used when a spectral response calibration is required. Accurately calibrated tungsten lamps are relatively expensive and generally do not have long term stability. To circumvent this problem, a method has been developed for which noncalibrated tungsten lamps may be used as reference light sources for calibrating the spectrometer wavelength response when the true tungsten filament temperature of the reference source is equal to the unknown source temperature. Then, a plot of the proper qualities vs the lower energy level of the spectral lines provides the source temperature. The absolute calibration of the tungsten lamp is not required.