高动态性能精密电容检测电路设计

High Resolution Capacitance Measurement Technology Used in Capacitive Sensor

从电路噪声的角度分析了直流充放电法和交流激励法电容测量技术的性能,得出交流法在增加电路复杂度极小的条件下,可获得较高的电容分辨率.给出了采用交流法的电路设计.使用Σ/Δ模数转换器,在获得高精度的A/D转换结果的同时简化了低通滤波器的设计,并获得了可编程的动态性能.理论分析和实践证明,本设计满足了10-16F电容变化量检测的应用需求.

The DC charge based and AC based capacitance measurement technologies are analysised from the point of noise performance,which is the key factor to determine the resolution of measurement.The conclusion that AC based technology can get higher resolution with little increasing in circuit complexity is drawn by comparing the circuit performance and structure of the two technologies.The AC based measurement is adopted.The applying of the Σ/Δ A/D converter simplifies the low pass filter design,gets high resolution and programmable dynamic performance.The theory analysis and experimentation prove that the technologies applied in the system are proper for the measurement demand of 10-16 F capacitance variation.