Onsite Calibration Of The Precision Industrial Platinum Resistance Thermometer Based On Gallium And Gallium Based Small-size Eutectic Points

Temperature is one of the seven principal parameters of the International System of Units.The magnitude of the temperature measurement is accurate or not, relating to the level of temperature measurement of the national defense and people's livelihood.At present, the international temperature scale level is a few milli-Kelvin, but the actual level of industrial application is several times, even hundreds of times,than the temperature scale level several times.There is a larger gap between temperature scale and the actual level of scientific research and industrial application level.The reference fixed point transfer technology applied to site temperature calibration,which is an international trend. In order to solve the precision platinum resistance thermometer calibration issue in the industrial field, China Institute of Metrology is committed to research the feature of the micro eutectic point, developed portable multi-point auto-reproducing apparatus.The small-size eutectic points are including Ga-In(15.7 ?), Ga-Sn(20.5 ?), Ga-Zn(25.2 ?) and Ga fixed point(29.7 ?).We developed two sets of portable multi-point auto-reproducing apparatus(constant power device and temperature control device).Based on gallium and gallium based small-size eutectic points of precision platinum resistance thermometer calibration method, is used to enhance the level of on-site calibration of precision platinum resistance thermometer.This research will offer the technique supports for the onsite calibration of temperature sensor of blackbody for infrared remote sensing satellite.The results show that both constant power and temperature control device, Ga-In Ga-Sn, Ga-Zn eutectic point and the point of Ga's temperature plateau continued 2 hours, reproducibility of less than 5 mK. Analysis of experimental results are summarized in three kinds of practical calibration method- comparison?turning points and constant temperature plateau method, The reproducibility first two methods are less than 5 mK.Since the research facility will be applied to in-orbit calibrationof the spaceborne standard radiation source,we studies degree of supercooling of gallium eutectic point and the point Ga is particularly important.It was found that several factors of the degree of supercooling of the micro gallium can be changed.Such as gallium melt point of holding time, cooling rate of gallium melt point, the superheat of gallium melt point, It has a significant size effect when solidified gallium,add impurity carbon powder,change the surface roughness of gallium crucible and so on.To verify the results and provide guidance for improving experimental device,we used ANSYS finite element analysis software to simulate the process of micro gallium melting point.We can found that gallium melting point temperature of 29.3 ?and the simulation of gallium melting point temperature(29.5 ?),which have difference of 0.2 ?.The process of simulation can clearly describe the process of melting point of gallium.We simulatedthe soaking blocks, and draw a conclusion of temperature distribution and the heatingtemperature gradient.