| In physics, temperature is a physical property of a system that underlies the common notions of hot and cold. Temperature is one of the seven principal parameters of the International System of Units. The temperature measurement is widely used in energy, metallurgy, manufacturing, electronics, new materials, health care, defense, aerospace and scientific research. It goes without saying that the accurate measurement is very important to science & technology research and industrial applications. Particularly, near room temperature, the high precision temperature measurement becomes more and more important in biotechnology, marine and semiconductor industry. And the melting temperature of gallium is 29.7646℃, which matches well with current technological development.In this paper, the reproducibility and stability are investigatied in depth, based on the latest developed devices of the gallium melting point by the National Institute of Metrology. The aim is to increase the level of our national temperature baseline and ensure the accuracy and reliability of the value transfer in this temperature field. At the same time, it also can be laying a solid foundation for the implementation of the fixed point impurity impact studies successfully and international comparison.Based on the new successful developed gallium melting point auto-reproduction device, first of all, the temperature plateau of the melting point of gallium is reproduced by two-liquid-solid interface method, the reproduction values are measured under different temperature plateau six times and compared with the domestic and international gallium melting point reference. Secondly, the stability of the melting point of gallinm is deeply study from four parts:First, adding air, water, alcohol and white mineral oil four kinds of thermal media in container thermometer well, the temperature reproducibility and the changing of thermometer resistance with different media are carried out at the same setting temperature; Second, we have experiments about the influence of different methods of reproduction on the reproducibility gallium melting point: at the same temperature conditions, the thermometer resistances are measured when the container is melted and not; Third, carrying out the research experiment that the effect of different external heat transfer conditions on the reproducibility of the gallium melting point: the gallium melting point reproduction container is reproduced at 30.1℃,30.6℃,31.1℃and 31.6℃, and the temperature plateau curves are compared.Fourth,on the one hand, by doping with different concentrations of impurity tin in the gallium fixed point cell, the value is reproduced and the relationship between impurity concentration and the variation of fixed point temperature is obtained; on the other hand, through the thermal process the experimental analysis is carried out on the melting temperature plateau, and the effect of impurities on the the fixed point temperature is also investigated.Lastly, the uncertainty of the reproducing device of gallium melting point is analyzed. Lastly, the uncertainty of the reproducing device of gallium melting point is analyzed.The principal analysis results are shown as follows:the reproducibility of the gallium melting point device is better than 0.06 mK, and the expanded uncertainty is 0.36 mK; in the experiment that the effect of four different media on the stability of gallium melting point, the influence of water, alcohol and white mineral oil is consistent, while the air is 0.2mK less than the first three; after reproduced the gallium melting point in four different temperature, the maximum temperature plateau is obtained at 30.6℃and the temperature plateau volatility is within 0.1 mK; the reproduction values with water at 40℃and 50℃as internal re-melting media are 0.01 mK and 0.02 mK lower than not within the melt, respectively; when the incorporation of metal tin is within 1.5%, the reproduction value of gallium melting point is increased with the quality of the metal tin. |
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