Research On The Influence Of Environment Parameters In The Inertial Mass Measurement Project

The redefinition of the mass unit kilogram requires accurate measurement of the value of Planck constant.The inertial mass measurement project is an electric balance method that obtains the Planck constant measurement by measuring oscillation period of the balance system.Its obvious feature is that the mass involved in the measurement process is inertial mass,which is different from other Planck constant measurement methods basing on gravitational mass.By measuring the change of the oscillation period of the balance under different weights and different voltages loaded on the capacitors,the connection between the electrical unit and the SI unit is established,and then the values of inertial mass and the Planck constant are derived.The measurement uncertainty of the Planck constant of the inertial mass measurement project is 4.5×10^-5.The accurate measurement of Planck constant by the inertial mass measurement project requires stable and accurate mechanical parametersβ₁ andβ₂ of the balance and quadratic coefficient k₂ of the capacitor fitting curve.In order to reduce the influence of environment parameters on the measurement results,the following studies are carried out in this thesis:First,the influence mechanism of temperature field fluctuation on beam deformation of the balance is studied,the model of the relationship between the oscillation period and the temperature field fluctuation is established,and the correction method of the temperature field fluctuation to the oscillation period is proposed.Secondly,The refractive index compensation model is established to compensate the vertical displacement of the free electrode of the system of capacitor by studying the variation of atmospheric parameters of the laser optical path,and to improve the accuracy of the measurement of the capacitance coefficient.Thirdly,the atmospheric parameter monitoring system of the inertial mass measurement project and the upper computer software are developed to monitor the temperature（0.1℃）,humidity（3%RH）and air pressure（3h Pa）in real time,and realize the automatic correction of the measurement of oscillation period.Finally,based on the above research,this article proposes that the influence of temperature fluctuation could be reduced by improving the isolation cover of the system,the influence of the fluctuations of environment parameters on the measurement of the quadratic coefficient of the capacitance curve could be reduced by changing the laser optical path for measuring the displacement of the free electrode.These measures contribute to the reduction of the uncertainty of measurement of the Planck constant.