Research On Measurement Of Material's Spectral Emissivity

Emissivity is a physical quantity for the ability of heat radiation from object, is an important physical parameter. It is main parameter influences the thermal radiation capacity and the spectral distribution of objects. It is significant to develop an accurate apparatus to measure sample and study the standard sample for the measuring emissivity of special materials in industry and set up the standard database of thermal properties in China.This study seeks to establish a standard measurement of material's spectral emissivity. According to the definition of emissivity, the absolute measuring method was applied. The grating monochromator was chose to establish a high-precision measurement standard, because the simple measurement model, although it was very difficult to achieve. The apparatus has the ability to measure the normal spectral emissivity and calculate the total emissivity, also has a certain angle between the measuring direction and the normal direction on sample's surface. The normal spectral emissivity of a stainless steel oxide sample was measured at temperatures from 473K to 1000K and spectral range between 2μm and 15μm. Also the uncertainty analysis of measurements are report, the combined standard uncertainties for measurement is smaller than 0.04.The device uses monochromator to spite light continuously. The monochromator has narrow bandwidth characteristics conducive to the measuring materials with strong spectral selectivity. The signal-to-noise ratio of comparison measure between the sample's spectral radiance and blackbody's is improved by the Lock–in Amplifier and statistical measure method. Based on the double-temperature-blackbody method, the linearity of detection system responds spectral radiance is evaluated. In order to reduce the measurement uncertainty, a new method to calibrate thermocouple is proposed. Moreover, theoretical analysis and experimental research are made for the effect caused by second order spectrum of monochromator and stray radiation. Above innovative ways are play an important role on the studying methods of measurement and improving the precision of measurement.In this paper, mathematical model and standard device are established. The theoretical analysis and experimental research on performance of the measurement system was described detailedly. Also the uncertainty of measurement was evaluated.