传统测量微电阻的方法操作繁琐,且引线电阻和触点电阻对测量结果影响较大.本文设计的基于交流恒流源激励的微电阻测试仪由交流激励源、数字移相电路、信号调理电路以及A/D转换与显示电路等四部分组成.微电阻由交流激励源注入交流信号后通过高阻低噪声运算放大器AD620提取响应信号,再经过锁相放大电路测得其真实的响应电压,锁定后的信号克服了内部噪声和外部电磁干扰的影响,能够实现对微小电阻的准确测量.通过对样机的测试和比对标称值,该测试仪工作稳定,具有较高的测量准确度,方便携带和使用.%Operation of traditional methods of micro resistance measuring are complicated,and it has great influence on result of the micro resistance testing. The designed micro tester AC constant current source excitation based on the tester by AC excitation source,digital phase shifter circuit,signal conditioning circuit and A/D conversion and display circuit is composed of four parts. Micro resistance by AC excitation source into AC signal through high impedance low noise amplifier AD620 to extract the response signal,and then after AD630 phase-locked amplifier circuit which measured the true response voltage signal after locking to overcome the influence of noise and external electromagnetic interference in a large extent,can realize the accurate measurement of small resistance. Through the test and comparison of the prototype nominal value,results show that the instrument works stably,has high measuring accuracy,convenient to carry and use.
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