A packaged pyrometer for high temperature gases

A packaged, automated instrument for temperature measurement in high temperature gases has been developed. The instrument is based on the well established method of spectroscopic emission-absorption pyrometry or line reversal. The instrument is intended for use with gases seeded with alkali metals in the temperature range 2000-3000K. Provision has been made for simultaneous measurements at multiple wavelengths, which extends its use to the case of flows containing scattering particulates. The basic measurement is made by transilluminating the gas with radiation from a calibrated tungsten lamp of known brightness temperature. The signal from the lamp plus gas emission together with that from the gas alone and that from the reference lamp are brought sequentially to a spectrally selective detector. The gas temperature is then calculated, using the second radiation constant and the measurement wavelength which is chosen on or close to an absorption line, such that the optical depth is less than or equal to 1. An analysis has been made to extend this method to compensate for the presence of scattering particulates, and also to measure the particle temperature