基于正交锁相放大器的交流电法接收机设计

Design of AC electrical prospecting receiver based on orthogonal lock-in amplifier

针对目前野外测量环境复杂,直流电法仪测试结果不稳定、发射电流大导致野外使用不方便等问题,提出将相关检测技术用于低频交流电法接收机的设计方案。采用正弦波交流激发,通过正交锁相放大器测量接收电极上电位差信号的幅值和相位信息,实现复电阻率的低频交流电法仪接收机设计。利用中心频率自动可调的带通滤波器和频率自动跟踪的锁相放大器,在强噪声背景下检测出接收电极上的电位差信号。实验结果表明:在一定频率范围内接收机实现频率自动跟踪测量,准确测量出被测信号的幅值和相位,提高电法仪的测量精度和抗干扰能力。

A design plan of using a new inspection technology for low-frequency AC electrical prospecting receiver has been proposed in this paper to substitute the present DC electrical method that has unstable test results and large emission current when used in complicated field measurement environment. A low frequency AC electrical prospecting receiver with complex resistivity is designed through AC sine wave excitation and the measurement of amplitude and phase information of potential difference signal on a receiving electrode by an orthogonal lock-in amplifier. The receiver can detect potential difference signal of the receiving electrode under strong noise background with the help of an automatic frequency-tracking lock-in amplifier and a center frequency-tunable band-pass filter. The result shows that the receiver has implemented automatic frequency tracking measurement in a certain frequency range, has accurately measured the amplitude and phase of the signal tested,and has improved the measurement accuracy and antijamming capability of the electrical prospecting instrument.