A spherical plate capacitive displacement sensor was designed.Spherical probe plate structure not only eliminates the effects of edge effect on principal,but effectively solves the problem of alignment in traditional parallel plate capacitor. Weak capacitance detection circuit based on AD7747 has high integration,good stabilty,and can effectively realize digital capacitance measurment.Static calibration experiments for the designed sensor were carried out,fitted the nonlinear relationship between ca-pacitance and displacement by the method of least squares polynomial fitting.The results show that spherical plate capacitive dis-placement sensor is with an effective diameter of 1.25 mm,stability can reach 0.002 pF / 20 min,maximum repeatability error is 0.219％ in range of 0.5 to 100 μm,resolution can reach 20 nm within 10 μm measurement range.%设计了一种球型极板结构型式的电容式位移传感器.球型极板结构探头既能从原理上消除边缘效应带来的影响,又有效解决了传统平行板电容传感器的对中问题.以AD7747为核心的电容检测电路,集成度高,稳定性好,能够有效实现电容测量的数字化.对所设计传感器进行静态标定实验,通过最小二乘法多项式拟合方法对电容值与位移间的非线性关系进行拟合处理.结果表明:有效直径为1.25 mm的球型极板电容位移传感器,在20 min、0.5～100μm测量范围内稳定性能够达到0.002 pF,最大重复性误差为0.219％,在10μm测量范围内,分辨力能够达到20 nm.
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