设计了基于数字电路方法,采用电容数字转换芯片AD7745和高性能ARM微控制器为核心的信号测试电路.给出了AD7745的测量原理和电路的软硬件设计.AD7745直接将微弱的电容信号转换成数字信号而非电压信号,避免了将有用电容信号同误差电容信号一起转换成电压信号,有效降低了环境中分布电容和寄生电容的干扰.实验结果表明:设计的微位移电容传感信号处理电路提高了变极距型电容传感器的稳定性和抗干扰能力,实现了0.72 μm的分辨力.%Based on digital circuit design methods, a signal test circuit is designed by using the capacitance digital conversion chip AD7745 and high-performance ARM micro-controller. The measurement principle of AD7745 and the software and hardware design of circuit are described. AD7745 directly converts capacitance signal into digital signal rather than voltage signal, which can avoid converting the useful signal together with the error signal into voltage signal, and effectively reduces the interference of distributed capacitance and parasitic capacitance in environment. The experimental results show that the signal processing circuit for micro-displacement capacitance sensing improves stability and anti-interference ability of variable pole pitch capacitive sensor,and the resolution of the system is up to 0. 72 μm.
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