In order to measure the temperature of surface treated steel strips at a low temperature range by radiation thermometry, the following items were investigated;
(1)Shielding method of stray radiation energy from environment.
(2)Estimation method of emissivity of measured objects.
This stray radiation energy has been eliminated by a water cooled shielding flange. And, a new emissivity measuring system has been developed. The system uses a radiation source to irradiate the measured object surface. This radiation is reflected and scattered by the object surface. The system has three detectors, and these detect scattered radiation energy by different solid angles. Hemispherical reflectance of the object surface is calculated by these three detected radiation energies, and the emissivity of the object surface is estimated by means of Kirchhoff's law. The estimated emissivities are compared with values measured by a spectrometer. The results show the obvious relationship between measured values by this system and these by spectrometer.
