介电常数法在墙体水管探测中的应用

Application of Dielectric Constant Method to Detection of Water Pipe in Walls

文中利用水与建筑材料介电常数差异很大的特点,设计了一款电容传感器用于墙体水管探测.基于空间静态电场的拉普拉斯方程建立了电容传感器的探测模型,通过松弛迭代进行解算,得到了传感器输出电容随被测水管位置的变化规律.文中还基于脉宽调制法设计电容传感器的测量电路,并利用模糊PID控制单元调节电路激励电压,以保证测量电路快速进入工作状态.针对该传感单元,设计了墙体中水管的中心检测算法.测量结果表明,PID控制单元可以迅速、准确地完成测量电路激励电压调节,以使传感器适应不同的工作环境,系统能在120mm厚度墙体内完成水管探测,并在70mm厚度墙体内可以完成中心定位.

Based on the great difference in dielectric constant between water and building materials,a capacitive sensor for the detection of water pipe in walls is proposed. In the investigation,first,a detection model of capacitive sensor is established on the basis of the Laplacian equation in spatial static electric field. Then,the model is solved via the relaxation iteration,and the relationship between the output capacitor of the sensor and the position of the detected water pipe is acquired. Moreover,the measuring circuit of the capacitive sensor is designed on the basis of the pulse width modulation,with its exciting voltage being adjusted by a fuzzy PID controller unit. Thus,the measuring circuit can evolve into the working condition as soon as possible. Finally,a center detection algorithm of water pipe is designed for the proposed sensor unit,and the corresponding measurement is carried out. The results show that the PID controller helps to adjust the exciting voltage in the measuring circuit rapidly and accurately, which makes the sensor to be effective in different working conditions;and that the proposed system can detect the water pipe in a wall with the thickness of 120 mm and locate the center axis of water pipe in a wall with the thickness of 70mm.