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用电容式传感器测量振幅有一个缺点,就是测量灵敏度会随着传感器探头与振动体之间的距离(lift-off)而变化。本文描述一种适用于工业测量、振幅范围为1～l00mμ的测量装置。为使灵敏度不随距离变化,对振动体和传感器探头提供了串联的两种电源。一种是直流电源,另一种是交流(高频)电源。通过低通和高通滤波器把最后合成信号分离成两个信号。低频成分(eoL)与振幅成正比,而与距离的平方成反比;高频成分(eoH)与距离成反比。通过在电路上进行的运算,就可实现距离补偿。当传感器探头有效面积为4.11mm~2时,对距离从0.2mm到2.0mm进行补偿后可以使误差小于5％。
One of the disadvantages of measuring amplitude with a capacitive sensor is that the measurement sensitivity varies with the lift-off of the sensor head and the vibrating body. This article describes a measurement device suitable for industrial measurement with an amplitude in the range of 1 to 100 mμ. In order not to change the sensitivity with distance, the vibrator and the sensor probe are provided in series with two power supplies. One is the DC power supply and the other is the AC (high frequency) power supply. The final composite signal is separated into two signals by a low-pass and high-pass filter. The low frequency component (eoL) is proportional to the amplitude and inversely proportional to the square of the distance; the high frequency component (eoH) is inversely proportional to the distance. Distance compensation can be achieved by performing calculations on the circuit. When the sensor probe effective area of 4.11mm ~ 2, the distance from 0.2mm to 2.0mm after compensation can make the error less than 5%.