| The quantitative observation level of spaceborne infrared remote sensing load needs to be maintained by high-precision spaceborne calibrated blackbody radiation source,and the measurement performance of calibrated blackbody radiation source is determined by the uniformity of axial temperature of the blackbody cavity,stability,brightness temperature accuracy and other parameters.These values need to be traced using the Precision Platinum Resistance Thermometer(PPRT).This thesis focuses on the high-precision calibration method of PPRT.The main contents include:Introducing the temperature traceability theory involved in calibration of PPRT.Analyzing the feasibility of PPRT calibration based on the principle and dividing method of the International Temperature Scale of 1990.Determining the melting temperature plateau used in fixed-point phase transition characteristic experiment and the calibration experiment scheme of thermometer according to the fixed-point phase transition theory.Introducing the sources of measurement uncertainty of PPRT according to different experimental methods.Studying the temperature calibration method of miniature fixed-point device,and calculating the mathematical relation between the measurement value of miniature fixed point and that of standard fixed point through experiments,so as to realize the direct temperature value transfer to PPRT.The experimental results show that: there is a ± 2.4 m K difference between the modified micro-gallium fixed-point and the standard-gallium fixed-point,and there is a ±3.3 m K difference between the modified micro-mercury fixed-point and the standard-mercury fixed-point.Improving the standard calibration equation to make it more flexible,portable and widely used.The experimental results show that: the error of(-38.83444 ～ 0.01)℃temperature region deviation equation extrapolated to-189.3442℃ is 5.2 m K,and the error of(0 ～ 29.7646)℃ temperature region deviation equation extrapolated to156.5985℃ is 2.0 m K.Meanwhile,the error of the data processing model based on the comparison method is 0.4 m K at-189.3442℃ and 2.9 m K at 156.5985℃.Assessing the measurement uncertainty of PPRT.If the PPRT is calibrated by the fixed-point method,the evaluation content is as follows: the extended uncertainty of water triple-point U = 4.4 m K,k = 2;the extended uncertainty of micro-gallium fixedpoint U = 6.7 m K,k = 2;the extended uncertainty of micro-mercury fixed-point U =12.2 m K,k = 2.If the PPRT is calibrated by the comparison method,the evaluation content is uniformly distributed at 9 temperature points in the measured temperature range,and the extended uncertainty range is(3.9 ～ 4.9)m K,k = 2.The evaluation results of measurement uncertainty directly show the PPRT level of the project calibration and the reliability of the thesis data. |
