用于电磁法观测系统开机自检的信号发生器实现方法

针对电磁法观测系统在使用过程中的开机自检要求,分析常用测量系统及地球物理仪器的检测信号特征,通过对已有机制进行研究和对比,结合现有信号产生电路的优势,提出一种功耗低、精度高、设计简单的自检信号发生器实现方案.基于该方案设计了一套实现电路,其以CPLD为核心,由精密参考电压源、模拟开关及运算放大器等器件构成,并对该电路进行仿真与测试.通过系统稳定性分析,采用波特图与奈奎斯特图表明信号发生电路的稳定性符合设计要求.经仿真与测试,能够通过换挡开关产生幅值为20μV～2 V、频率范围在1 Hz～100 kHz的自检脉冲信号,频率稳定在1%,重复测试相位稳定度小于1.5%,幅值误差可以优化到1%以内,且能通过其稳定的谐波分量来获取该系统带宽更宽的通道测试响应.测试结果表明,该自检信号发生器电路实际功耗小于0.3 W,20μV～2 V幅值范围和1 Hz～100 kHz频率范围内性能指标的测量结果和仿真结果相符,并成功应用于某监控系统.利用该信号发生器电路实现自检具有操作方便、成本低、易于设计等优点,能够有效的弥补其它自检模式的缺陷.

A realization of signal generator used in boot-strap self-test of electromagnetic prospecting systems

To meet the boot-strap self-test requirements of electromagnetic prospecting systems, the characteristics of self-test signals of commonly used geophysical instruments and measurement systems are analyzed. Through doing comparison and analysis on existing mechanisms, a novel method is proposed with low-power consumption, high precision, as well as easy realization. A set of implementation circuit is designed and simulated. The circuit is shown to have a strong stability on the basis of Bode and Nyquist diagrams. The simulation and test results show that a self-test pulse with a range of 20 μV~2 V amplitude and 1 Hz~100 kHz frequency can be generated through switches. And the signal frequency stabilizes at 1%; phase stability is no more than 1.5% through repeated test, and amplitude error can be optimized to less than 1%. Using the stable harmonic component of the self-test pulse signal, a response in wider band of the measurement system can be obtained. The practical application demonstrates that the boot self-test model has a power consumption less than 0.3 Watt; and an amplitude between 20 μV and 2 V, and frequency range of 1 Hz~100 kHz. This is consistent with the simulation. The self-test model is applied to a monitoring system. The model has the advantages of stable performance, convenient operation, low cost, and easy-to-design. It can improve present self-test models.