The Design And Implementation Of Automated Realization System For National Low-Temperature Standard Fixed Points

Temperature measurement and control technology is widely used in such as industrial production,aerospace,meteorological early warning,oil drilling and transporation and other fields.Low temperature(under 273.16K)technology and cutting-edge scientific research are closely related,such as super conducting technology,aerospace technology,high-energy physics,controlled thermonuclear fusion and so on.So the accuracy of the transmission of the low temperature is the basis for the development of these fields.The realization device for national standard in the temperature range from 13.8033 K to 273.16 K in NIM still used liquid helium to provide the constant temperature and cold environment and there are some problems with the device,such as uneven temperature field,the low efficiency of reproduction,low accuracy and so on.This device has been unable to meet the requirements of the national standard.In foreign,the realization of low-temperature fixed point has already realized the automation of the whole process,not only improves the reproduction efficiency,but also improve the accuracy of reproduction.This topic mainly aims at transforming the realization device for national standard in the temperature range from 13.8033 K to 273.16 K in NIM,use the high performance refrigerator to replace the liquid helium to provide the constant temperature and cold environment.The new device use the quasi adiabatic method to realize the triple point of equilibrium hydrogen,neon,oxygen,argon in the same cryostat.Finally,appraise the performance of the new realization system for national low-temperature standard fixed points and check the new realization system whether meet the requirements of the national standard and thebilateral comparisons.The main work is as follows:(1)Develop a device based on refrigerator for realization of fixed points.The device use refrigerator to supply the constant temperature and cold environment and can realize these four fixed points in the same cryostat.(2)Develop an automatic control system based on virtual instrument.The functions of the LabVIEW program are temperature control,pulse heating and temperature measurement.Integrate the high-precision electrical measurement equipment and complete the build of control system.The program improve the work efficiency and accuracy.(3)Realize these four fixed points and appraise the performance of the new realization system.Use the new system to realize the triple point of equilibrium hydrogen,neon,oxygen,argon,the reproducibility are 0.05 mK,0.02 mK,0.03 mK,0.05 mK,and the standard uncertainty of the four fixed points is better than 0.1mK.The new realization system establishes the foundation for bilateral comparison with IMGC.