基于自由轴法的智能RLC测量仪研究

Research of Intelligent RLC Measuring Instrument Based on Free-axis Method

为解决电阻R、电容C、电感L元件参数测量过程中自动换档、类型识别和测量精度问题,提出一种改进的自由轴法智能RLC测量仪设计方法。在方法上,使用自由轴法解决固定轴法中所要求的测量电路激励信号与基准信号具有固定相位关系的问题;采用脉冲积分鉴相法解决乘法鉴相法中直流电平易漂移的难题。在电路实现上,测量电路采用8级基准参考电阻、差分仪表放大等改进电路结构提高测量精度;脉冲积分鉴相采用模拟开关正交鉴相、差分提取投影标量提高电路性能。实测结果表明:该RLC测量仪结合自适应换档算法,能实现量程内各种元件参数测量的自动换档、元件属性自动识别,电阻测量范围10Ω~1 MΩ内,精度0.5%;电容测量范围50 p F^470μF内,精度2%;电感测量范围50μH^10 m H内,精度5%。

In order to solve some problems in traditional RLC（ resistance,capacitance and inductance） parameter measuring instrument,such as automatic shift,character recognition,measure precision and so on,an improved intelligent RLC measuring in-strument using free-axis method was proposed.In free-axis method,the phase relation between excitation signal and reference signal was not restricted,which was absolutely different from the fixed-axis method.The pulse integrator phase detecting method was adopt-ed to solve DC drift problem in multiplier phase detector.Higher accuracy was obtained in the measurement circuit by using 8 range reference resistors,difference instrumentation amplifier and the improved measurement structure.The circuit performance was im-proved in the pulse integrator phase detector, which was composed of analog switch detecting orthogonal phase and differential cir-cuit extracting the projection coordinate.Experimental results show that the instrument combining adaptive algorithm can achieve automatic measurement and character recognition.Resistance measurement range is from 10Ωto 1 MΩ,and the accuracy is 0.5%. The capacitance measurement range is from 50 pF to 470μF,and the accuracy is 2%.The inductance measurement range is from 50μH to 10 mH,and the accuracy is 5%.