交流电阻及其时间常数的准平衡式电桥精密测量技术

Precision Measurement of AC Resistance and Time Constant Based on Quasi-Balance Resistance Bridge

研究了一种基于准平衡式电桥的交流电阻及其时间常数精密测量方法。电桥以双级感应分压器为比例参考标准,利用电子线路将电桥不平衡差值电压转移至变压器绕组,自动实现电桥准平衡状态,消除了感应分压器比例绕组内负载的影响。将数字同步采样测量方法应用于阻抗测量,实现了交流小电压复数比的准确测量。采用电子式引线电压补偿技术和开尔文网络消除了小电阻测量时串联导线的影响。研制的交流电阻及其时间常数测量装置可测量1~10 000Ω范围内交流电阻,测量频率为1 k Hz时实验结果表明,测量装置具有较高的准确度和稳定性。

The method of precision measurement of AC resistance and time constant based on a kind of quasi-balance resistance bridge is studied. A two-stage inductive voltage divider is used as the ratio reference of the bridge. The unbalanced bridge voltage is transferred to winding of a transformer by electronic circuits,realizing the quasi-balance status automatically of the bridge. The quasi-balance state also makes the voltage ratio of inductive voltage divider unaffected by internal loading of ratio winding. The digital synchronous sampling method is used to measure the small complex voltage ratio. To reduce influence of lead wire connecting two resistors when measuring small resistors,amplifiers are used to eliminate voltage drop on the wire together with a Kelvin network. The measurement system designed in this paper can measure resistance from 1 Ω to 10 000 Ω.Experimental results at frequency of 1 k Hz show that the measurement system deserves high accuracy and stability.