【作者】 王雪；

【导师】 颜华；

【作者基本信息】 沈阳工业大学 ， 检测技术与自动化装置， 2012， 硕士

【摘要】 电容层析成像(ECT)技术是过程层析成像技术的一种,因其结构简单,成本低,非辐射,非侵入,响应速度快等优点,得到广泛的研究和应用。ECT技术通过电容传感机理,为图像重建提供投影数据,获取密闭管道或容器内的二/三维可视化信息。ECT系统中电容数据采集方法各异,较多采用分立元件实现,为了建立集成化,结构更为简单,性能优良,更适合工业现场应用的电容数据采集系统。本文研究CDC技术在微小电容检测中的应用,以CDC技术为基础,建立ECT数据采集系统。论文分析了ECT数据采集系统中,电容检测的难点和要解决的主要问题。对以往的电容采集解决方案进行分析比较。研究CDC技术的原理及在微小电容检测上的应用。并深入研究CDC技术在ECT系统中应用的可行性。以CDC芯片AD7745为核心,建立ECT数据采集系统。由AD7745构建集成化的电容检测及信号处理电路。利用该电路提供高分辨率测量,并解决抗杂散和耦合电容补偿等问题。制作12极板直接三维电容传感器。研究极板选择方法,采用16-8矩阵式模拟开关CH446Q作为极板选择电路,避免复杂开关阵列式控制。以单片机为控制核心,建立ECT数据采集系统实验平台。设计上位机软件进行数据读取,上下位机采用串行通讯方式。完成软硬件调试,采集数据,并分析系统性能。实验结果表明,该系统有较高的精度和分辨率。电容测量值可以稳定到0.001pF。系统线性度和稳定性好,有杂散电容抑制能力和一定范围的耦合电容补偿能力。基于CDC技术的ECT数据采集系统是ECT技术具有研究价值的发展方向。更多还原

【Abstract】 Electrical Capacitance Tomography (ECT) technology is one kind of process tomography technology; it has been widely studied and applied because of its simple structure, low cost, non-radiation, non-invasive, fast response, etc. By capacitive sensing mechanism, ECT technology provides projection data for image reconstruction, obtains two or three dimensional visual information of pipe or vessel. The data acquisition methods are different in ECT system, most of them achieved by discrete components. In order to establish an integrated, more simple structured ECT data acquisition system with excellent performance and more suitable for industrial field application, this paper researches the applications of CDC technology in small capacitance detection, establishes ECT data acquisition system based on CDC technology.This paper analyzes the difficulties of capacitance detection and the main problems need to be solved in ECT data acquisition system, researches the principle of CDC technology and its applications in small capacitance detection, and analyzes the feasibility of CDC techniques in ECT system in-depth. An ECT data acquisition system using CDC chip AD7745 as the core has been established, it constructs integrated capacitance detection and signal processing circuit by AD7745, using this circuit, provides high-resolution measurement and resolved the issues of anti-stray and compensation of coupling capacitance and so on.A direct three-dimensional sensor with 12 plates has been designed in this paper. The paper analyzes the plate selection method, uses 16?8 matrix analog switches CH446Q as plate selection circuit which can avoid the control of complex array switches, establishes experimental platform of ECT data acquisition system using MCU as the control center. PC software is used for data reading. Upper and lower machines use serial communication. The paper has completes hardware and software debugging, data acquisition and the analysis of system performance.Experimental results show that, the system has high accuracy and resolution, capacitance measurements can be stabilized to 0.001pF. The linearity and stability of the system is good. There are abilities of suppression of stray capacitance and compensation of coupling capacitance in the system. We can see that CDC-based ECT data acquisition system is a development available for study.更多还原