Emissivity-free radiation thermometry for high-temperature metals using the dual-wavelength reflectance-ratio method

This article describes a preliminary study verifying the applicability of the dual-wavelength reflectance-ratio (DWR) method to emissivity-free radiation thermometry for electromagnetically levitated high-temperature liquid metals. To establish the measurement technique, the DWR method was applied to inductively heated solid spherical Cu and Ni samples. Regardless of the differences in the sample emissivity values, the temperature determined using the DWR method agreed within 20 K with the temperature determined using a thermocouple. It was found that the temperatures of metallic samples having different emissivity values can be determined with a standard uncertainty of 8 K in terms of the absolute temperature when applying the DWR method, even if the sample has curvature and is exposed to high temperatures of up to 1250 K.