交流小电流测量是交流阻抗测量的关键技术之一。分析了交流小电流测量对交流阻抗测量的影响，提出采用数字相敏检波原理测量交流小电流的方法，利用互相关技术有效克服放大器噪声对交流小电流测量的影响，完成了交流阻抗测量的预期功能，达到了预期的效果。%AC weak current measurement is one of the key technologies in AC impedance measure-ment. Effect of the AC weak current measurement to AC impedance measurement is analyzed, the method of using Phase Sensitive Detector ( PSD) to measure the AC weak current is put forwarded, using cross-correlation technique the amplifier noise influence to AC current measurement is conquered, the ex-pected function of AC impedance measurement system is done and the desired accuracy is achieved.
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