Processing Method of Multi-Wavelength Pyrometer Data for Continuous Temperature Measurements

The processing of multi-wavelength pyrometer data is a problem that needs further improvements. The solutions developed in earlier decades generally assumed one particular mathematical relation for emissivity versus wavelength in the wavelength range of the measurements. Sometimes this assumption worked and produced acceptable results, but in many other cases this approach provided erroneous results. Individual results were strongly dependent on the assumed mathematical relation that often needed some prior knowledge of the emissivity behavior in the wavelength range. A new data processing method for a multi-wavelength pyrometer for continuous temperature measurements is presented. A linear relation between emissivity and true temperature at different wavelengths is assumed. Based on this assumption, the true temperatures and spectral emissivities at the two continuous temperature measurement points can be simultaneously calculated. Some experimental results for the practical data processing of measurements performed on a solid propellant rocket engine show that the difference between the calculated true temperature and the theoretical true temperature indicated by the rocket engine designer is within ±20 K. Paper presented at the Seventh International Workshop on Subsecond Thermophysics, October 6–8, 2004, Orléans, France.