Development of a Novel Pyrometer by Eliminating the Uncertainty of Emissivity Using Reflector with Two Apertures in Medium Plate Rolling Process

The uncertainty of emissivity has a major effect on the accuracy of a pyrometer in billet temperature measurement. In order to eliminate the influence of emissivity, we place a reflector with two apertures at the front of a pyrometer. The two apertures on the reflector are used to measure intrinsic radiation and approximate blackbody radiation of the billet. The radiation is collected by two infrared dual-band detectors in the pyrometer. Then, the real-time emissivity of the billet can be measured with no assumptions, so the influence of emissivity is eliminated. In addition, the measurement uncertainty is analyzed based on the ray-tracing method. The pyrometer is developed and the accuracy verification of emissivity is implemented. Compared with the reference material at the same temperature, the measurement errors of the emissivity are 0.021 and 0.005 at two wavelengths. Then, we install the pyrometer in the medium plate rolling process for measurement. Compared with a thermal imager used in the rolling process, the measurement fluctuation is reduced obviously. It indicates that the method of emissivity measurement is very effective for billet temperature measurement.