用于焦耳天平的两种直流互感测量方法的比较分析

Comparisons of Two Measurement Methods for DC Value of Mutual Inductance in Joule Balance

我国焦耳天平方案联系磁能量差和重力势能差来建立量子质量基准,直流互感的精密测量是此方案最为关键的技术之一.针对这一难题,近几年分别提出了低频交流外推法和标准方波补偿法来精确得到互感的直流值.在分析互感频率特性的基础上分别介绍了两种方法的测量原理,并对两种方法的测量结果进行了比较,同时分析指出了两种方法可能存在的问题和相应对策.目前初步实验结果表明,两种方法的一致性达到1.1×10-6.

Joule balance in national institute of metrology （NIM） relates the difference of magnetic energy and the difference of gravitational potential energy to establish the quantum mass standard. Mea- suring the DC value of mutual inductance precisely is one of key technologies in Joule balance. In recent years, several methods such as low-frequency-extrapolation method and standard-square-wave compensation method to obtain the DC value of mutual inductance are proposed. The analysis of the frequency characteristic of mutual inductance and the principles of two measurement methods are provided in this paper. Besides, the comparisons are made through alternate measurements, and further considerations for the two methods are pointed out. Preliminary experimental results show that the deviation between the two methods is only 1.1×10-6.