New Emissivity Measuring System with High Accuracy Under Controlled Environment Conditions

Accurate knowledge of spectral emissivity is very important in many technological and scientific applications. In this study, a new measuring system, which can realizes spectral directional emissivity measurements under controlled environment conditions, was constructed. The apparatus realizes the high accuracy emissivity measurement through the precision knowledge of the sample surface temperature and the high-precision calibration. The temperature of the sample surface is accurately measured by the suitable method depending on the sample type. Accurately determining the spectral response function and the background radiation are obtained by the modified two-temperature calibration method proposed in this study. The evaluation of the assisted blackbody shows that it has good temperature uniformity and high emissivity, which guarantee the effectiveness of the modified two-temperature calibration method. Spectral emissivity of silicon carbide was measured, and the conformity with literature data around the Christiansen wavelength proves the reliability of the developed apparatus. In addition, the spectral emissivity of copper during the real time oxidation was measured to check the capability of the emissivity measurements under controlled environment. Finally, the uncertainty for silicon carbide at 1073 K is evaluated, and the relative combined standard uncertainty for silicon carbide sample at 1073 K is better than 2.9 %.