计算电容屏蔽电极位移测量的不确定度评估

计算电容是电学阻抗单位复现的基准装置,是电容、电感和交流电阻的溯源依据.它是电磁计量领域内除量子电压、量子电阻基准之外准确度最高的装置.计算电容装置实现微小电容值(0.2至0.6 pF)精确测量的关键在于对其屏蔽电极位移的高准确度测量.从计算电容屏蔽电极位移测量的基本原理出发,系统分析了屏蔽电极位移测量结果的影响因素,...

Uncertainty Evaluation on Displacement of Blocking Electrodes in Calculable Capacitor

The calculable capacitor is a classical and fundamental experiment apparatus in precise electromagnetic measurements. It is followed the ‘new’ electromagnetic principle which is firstly introduced by Lampard D G and Thompson A E. The calculable capacitor is the AC impedance primary standard, and its the traceable source of the capacitance, inductance and AC impedance. It is a high-accuracy (at the level of 10-8) apparatus surpassed only by the quantum Josephson voltage and quantum Hall resistance experiments in the electromagnetic metrological field, and it is expected to reach the level of 10-9 through continual improvements and optimizations to improve the uncertainty level of electromagnetic metrology. The basic principle of the displacement measurement in calculable capacitor is presented, and impact factors, including Fabry-Perot interferometer locking, laser wavelength, residual index of refraction of air, cosine error and Gouy phase correction, are analyzed. Combining the repeatability of capacitance produced by calculable capacitor, a relative standard uncertainty of 4.7×10^-9 is obtained.