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这种简单的位移测量电路可以读出两块平行板之间的电容,并把它转变成与间隔距离成正比的频率输出。电容测量技术常常用于位移测量。例如,测量压力式鼓膜的位移和控制光学干涉仪的两个镜面的距离。但是这种电路的位移测量原理比其他方法先进,因为它有频率编码的输出和线性度好。平行板电容器是运放微分电路的一个组成部分(见45页下图)。压控振荡器把正弦波信号加在电容器上。振荡器的控制电压由
This simple displacement measurement circuit reads the capacitance between two parallel plates and converts it into a frequency output proportional to the separation distance. Capacitance measurement techniques are often used for displacement measurement. For example, measure the displacement of the pressure tympanic membrane and the distance between the two mirrors that control the optical interferometer. However, the displacement measurement principle of this circuit is more advanced than other methods because of its good frequency coding output and good linearity. The parallel plate capacitor is an integral part of the op amp differential circuit (see the figure on the next page). The voltage-controlled oscillator adds the sine wave signal to the capacitor. Oscillator control voltage from