四端对双螺线型计算电阻及其量值传递装置研究

提出将双螺线型计算电阻的定义改为四端对形式,建立其等效电路模型,分析计算了定义变更对交流阻抗引入的附加误差。提出一种计算机控制的电流比较仪电桥作为四端对双螺线型计算电阻量值传递装置,设计研制了基于乘法型数模转换器的数字式微差补偿器,研究了用于电流比较仪自动平衡的牛顿迭代算法。测量结果显示,1 592 Hz频率范围内四端对双螺线型计算电阻的交、直流相对差在1×10-7内闭合。将四端对双螺线型计算电阻的交、直流差传递给商用交流标准电阻,合成测量标准不确定度为1.7×10-7,满足交流电阻量值传递要求。

Study on four terminal pair bifilar helix calculable resistor and its quantity value transfer equipment

In this paper, the definition of Bifilar Helix Calculable Resistor (BHCR) is extended to four terminal pair (4TP) component. The equivalent circuit model of 4TP BHCR is established, the additional AC impedance error caused by the definition change is calculated and analyzed. A computer controlled current comparator bridge is proposed, which is used for the quantity value transfer of the 4TP BHCR. A digital error compensator based on 16 bit multiplying digital to analog converter is designed and developed. The Newton iterative algorithm used in the auto balancing of the current comparator bridge is studied. The measurement results show that in the frequency range below 1 592 Hz, the AC/DC resistance relative difference of the 4TP BHCR is below 1×10-7. The AC/DC resistance relative difference of the 4TP BHCR is transferred to a commercial AC standard resistor, and the combined standard measurement uncertainty is 1.7×10-7, which meets the requirement of AC resistance quantity value transfer.