电荷放大器对石英传感器动态特性的影响

用控制理论对压电石英传感器的等效电路、电压放大器、电荷放大器对压电式传感器动态特性的影响等进行了深入的分析与研究。通过对电压放大器与电荷放大器的系统传递函数的分析指出,压电电压测量系统可等效为1阶环节和2阶惯性环节。由于1阶系统的存在,导致系统不能测量直流信号和变化比较缓慢的信号。该电压测量系统的缺点可通过加电荷放大器来改善,此时压电电荷测量系统的稳态灵敏度为d/CF,它只依赖于电荷放大器的反馈电容,与石英晶体和连接导线的电容无关。从而指出为了充分利用石英传感器,应用时最好连接电荷放大器。

Influence of Charge Amplifier on Dynamic Characteristics of Quartz Sensor

According to the automatic control theory,the influences of the current equivalent circuit,the voltage amplifier and the charge amplifier on dynamic characteristics of a piezoelectric sensor are highly analyzed and investigated.Based on the analyses of the transfer functions for the voltage amplifier and the charge amplifier,it is pointed out that the transfer function of the voltage measurement can be demposed into two terms,that is,a first order system and a second order system.Because the first order system exists,the voltage measurement system cannot be used for measuring d.c.and slowly varying signals.This disadvantage is overcome by introducing a charge amplifier.The steady state sensitivity of the charge measurement system is d/C_F,which depends only on the feedback capacitance C_F of the charge amplifier,and is independent of transducer and cable capacitances.Therefore,in order to effectively employ piezoelectric effect,the charge measurement system with a charge amplifier is recommended.