基于CDC技术的ECT数据采集系统
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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。
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.
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。
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.
引文
[1] Beck M S,and Byars M, et al. Principles and industrial applications of electrical capacitance tomograghy. Meas.+Conrt., 1997, 30:197~200.
[2] Beck M S, Williams. Process tomograpy:a European innovation and its applications. Meas Sci&Tech, 1996, 7(3): 215～224.
[3] Dickin F J and Hoyle B S.Tomography imaging of industrial process equipment: techniques and application.IEE Proceedings-G, 1992,139(1):72~82.
[4]李海青,黄志尧.特种检测技术及应用.浙江:浙江大学出版社,2000.
[5]颜华.电容层析成象技术及在高炉快状区物料可视化监测中应用的基础研究:(博士学位论文).沈阳,东北大学,1999.
[6]夏靖波.电容层析成象在两相流参数检测中的应用:(博士学位论文).沈阳,东北大学,1998.
[7]颜华,王师.电容层析成像技术及应用.工业仪表与自动化装置,1999(3):22~25.
[8] Yang W Q. Electrical capacitance tomography-from design to application. Measurement+Control, 1995(28): 261~266.
[9] Fasching G E and Smith N S. A capacitive system for 3-dimensional imaging of fluidized-beds. Re- v.Sci.Instrum, 1991.
[10] Xie C G,et al. Electrical capacitance tomography for flow imaging-system model for develpoment of image reconstruction algorithms and design of primary sensors. IEE.Proc.G, 1992.
[11] W. Warsito and L.-S. Fan. Measurement of real-time folw structures in gas-liquid and gas– liquid - solid flow systems using electrical capacitance tomography. Chemical Engineering Science, 2001,56: 6455~6462.
[12] R Wajman, R Banasiak,et al. Spatial imaging with 3D capacitance measurements . Meas sci.echnol, 2006, 17: 2113~2118.
[13] W Warsito, Q Marashdeh and L Fan. Some comments on‘Spatial imaging with 3D capacitance measurements’. Meas.sci.technol, 2007,18:3665~3667.
[14] R Wajman, R Banasiak,et al. Reply to comments on‘Spatial imaging with 3D capacitance measur- ements’. Meas.sci.technol, 2007, 18: 3668~3670.
[15] Manuchehr Soleimani, Haigang wang,et al. A omparative study of 3D electrical capacitance tomography. International Journal of Information and Systems Sciences, Janu.2007, 3: 292~306.
[16] R Banasiak, R Wajman, and D Sankowski.“Three-dimensional nonlinear inversion of electrical capacitance tomography data using complete sensor model”, Progress in Electromagnetics Research. PIER100, 2010, 219~234.
[17]李海青,乔贺堂.多相流检测技术进展.石油工业出版社,1996:57~64.
[18]阎润生,刘石.电容层析成像算法的比较.仪器仪表学报,2004,25(4):619~620.
[19]许会,颜华等.气液两相流液相体积含量的精确测量.仪器仪表学报,1999,20(6):641~643.
[20]邵富群,高彦丽.考虑交互作用的ECT传感器的分析和优化.东北大学学报(自然科学版),2003,24(2):103~106.
[21]许会,金锋等.电容传感器场灵敏度的合理计算方法探讨.仪器仪表学报,1999,20(5):489 ~492.
[22]肖化,严杰,保宗悌.12电极电容层析成像的敏感场仿真研究.仪器仪表学报,1998,19(3):225~229.
[23]董向元,刘石.电容层析成像中通用迭代法的研究.仪器仪表学报,2006,27(1):23~25.
[24]陈德运,郑贵滨等.电容层析成像系统传感器的仿真分析及遗传算法图像重建.系统仿真学报,2004,6(1):152~154.
[25] Yang W Q. An appraisal of three electrical techniques. in Proceedings of ISMTMF’98, Beijing, 1998: 285~290.
[26]徐苓安.过程层析成像技术的最新进展一记第一届世界工业过程层析成像会议.世界仪器仪表与自动化,1999,3(5):34~37.
[27]赵进创.电容层析成像技术及在两相流可视化监测中的应用研究:(博士学位论文).沈阳:东北大学,2001.
[28]刘文宇,赵进创.电容层析成像中微小电容检测的研究.科技资讯,2006,27:4.
[29]陈重.电磁场理论基础.北京理工出版社,2003:10~36.
[30]陆耿,彭藜辉等.电容层析成像系统的实用化设计.计量学报,2004,25(3):241~260.
[31]林国美,冯新泸,管亮.基于CDC技术和虚拟仪器的液态物质相对介电常数测定仪的研制.化工自动化及仪表,2010,37(7):62~65.
[32]谢楠,陈汉良,陈卫民.电容传感器信号调理的新方法.自动化仪表,2005,26(3):31~32.
[33]王献峰,石东.基于CAV424的变压器油微水检测.电子测量技术,2007,30(6):186~188.
[34]丁振荣,陈卫民.基于CAV424的油品含水率在线测量仪的研制.工业仪表与自动化装置,2004,(5):26~27.
[35]马坚刚,张天宏,朱理化.基于AD7746的电容法间隙测量应用系统研究.传感器与微系统,2008,27(2):65~70.
[36]陈宝,胡晓兵,孙鸿.基于AD7745的电容差压传感器设计.传感器与微系统,2011,30(6):71~76.
[37]郭彦蕊,黄运生,陈学.AD7745在油井含水率检测电路中的应用.仪表技术,2009,(2):14~18.
[38]徐乐年,张磊,员玉良.基于CDC技术的电容式水平位移传感器.传感器与微系统,2010(29):112~115.
[39]赵建东,康乐.自动洗碗机的控制系统.国外电子元器件,2004(8): 4~6.
[40]郭强,谢康,姜海明,王浩.电容数字转换器AD7745的工作原理和应用.现代电子技术,2008(14):170~172.
[41]龙海南,张莉莉.AD7745型高精度电容数字转换器.国外电子元器件,2006(8):70~71.
[42] 24-Bit capacitance-to-Digital converter with temperature Sensor AD7745/AD7746.Analog Device, Inc, 2005.
[43] Wuqiang Yang. Key Issues in Designing Capacitance Tomography Sensors. Sensors,2006.
[2] Beck M S, Williams. Process tomograpy:a European innovation and its applications. Meas Sci&Tech, 1996, 7(3): 215～224.
[3] Dickin F J and Hoyle B S.Tomography imaging of industrial process equipment: techniques and application.IEE Proceedings-G, 1992,139(1):72~82.
[4]李海青,黄志尧.特种检测技术及应用.浙江:浙江大学出版社,2000.
[5]颜华.电容层析成象技术及在高炉快状区物料可视化监测中应用的基础研究:(博士学位论文).沈阳,东北大学,1999.
[6]夏靖波.电容层析成象在两相流参数检测中的应用:(博士学位论文).沈阳,东北大学,1998.
[7]颜华,王师.电容层析成像技术及应用.工业仪表与自动化装置,1999(3):22~25.
[8] Yang W Q. Electrical capacitance tomography-from design to application. Measurement+Control, 1995(28): 261~266.
[9] Fasching G E and Smith N S. A capacitive system for 3-dimensional imaging of fluidized-beds. Re- v.Sci.Instrum, 1991.
[10] Xie C G,et al. Electrical capacitance tomography for flow imaging-system model for develpoment of image reconstruction algorithms and design of primary sensors. IEE.Proc.G, 1992.
[11] W. Warsito and L.-S. Fan. Measurement of real-time folw structures in gas-liquid and gas– liquid - solid flow systems using electrical capacitance tomography. Chemical Engineering Science, 2001,56: 6455~6462.
[12] R Wajman, R Banasiak,et al. Spatial imaging with 3D capacitance measurements . Meas sci.echnol, 2006, 17: 2113~2118.
[13] W Warsito, Q Marashdeh and L Fan. Some comments on‘Spatial imaging with 3D capacitance measurements’. Meas.sci.technol, 2007,18:3665~3667.
[14] R Wajman, R Banasiak,et al. Reply to comments on‘Spatial imaging with 3D capacitance measur- ements’. Meas.sci.technol, 2007, 18: 3668~3670.
[15] Manuchehr Soleimani, Haigang wang,et al. A omparative study of 3D electrical capacitance tomography. International Journal of Information and Systems Sciences, Janu.2007, 3: 292~306.
[16] R Banasiak, R Wajman, and D Sankowski.“Three-dimensional nonlinear inversion of electrical capacitance tomography data using complete sensor model”, Progress in Electromagnetics Research. PIER100, 2010, 219~234.
[17]李海青,乔贺堂.多相流检测技术进展.石油工业出版社,1996:57~64.
[18]阎润生,刘石.电容层析成像算法的比较.仪器仪表学报,2004,25(4):619~620.
[19]许会,颜华等.气液两相流液相体积含量的精确测量.仪器仪表学报,1999,20(6):641~643.
[20]邵富群,高彦丽.考虑交互作用的ECT传感器的分析和优化.东北大学学报(自然科学版),2003,24(2):103~106.
[21]许会,金锋等.电容传感器场灵敏度的合理计算方法探讨.仪器仪表学报,1999,20(5):489 ~492.
[22]肖化,严杰,保宗悌.12电极电容层析成像的敏感场仿真研究.仪器仪表学报,1998,19(3):225~229.
[23]董向元,刘石.电容层析成像中通用迭代法的研究.仪器仪表学报,2006,27(1):23~25.
[24]陈德运,郑贵滨等.电容层析成像系统传感器的仿真分析及遗传算法图像重建.系统仿真学报,2004,6(1):152~154.
[25] Yang W Q. An appraisal of three electrical techniques. in Proceedings of ISMTMF’98, Beijing, 1998: 285~290.
[26]徐苓安.过程层析成像技术的最新进展一记第一届世界工业过程层析成像会议.世界仪器仪表与自动化,1999,3(5):34~37.
[27]赵进创.电容层析成像技术及在两相流可视化监测中的应用研究:(博士学位论文).沈阳:东北大学,2001.
[28]刘文宇,赵进创.电容层析成像中微小电容检测的研究.科技资讯,2006,27:4.
[29]陈重.电磁场理论基础.北京理工出版社,2003:10~36.
[30]陆耿,彭藜辉等.电容层析成像系统的实用化设计.计量学报,2004,25(3):241~260.
[31]林国美,冯新泸,管亮.基于CDC技术和虚拟仪器的液态物质相对介电常数测定仪的研制.化工自动化及仪表,2010,37(7):62~65.
[32]谢楠,陈汉良,陈卫民.电容传感器信号调理的新方法.自动化仪表,2005,26(3):31~32.
[33]王献峰,石东.基于CAV424的变压器油微水检测.电子测量技术,2007,30(6):186~188.
[34]丁振荣,陈卫民.基于CAV424的油品含水率在线测量仪的研制.工业仪表与自动化装置,2004,(5):26~27.
[35]马坚刚,张天宏,朱理化.基于AD7746的电容法间隙测量应用系统研究.传感器与微系统,2008,27(2):65~70.
[36]陈宝,胡晓兵,孙鸿.基于AD7745的电容差压传感器设计.传感器与微系统,2011,30(6):71~76.
[37]郭彦蕊,黄运生,陈学.AD7745在油井含水率检测电路中的应用.仪表技术,2009,(2):14~18.
[38]徐乐年,张磊,员玉良.基于CDC技术的电容式水平位移传感器.传感器与微系统,2010(29):112~115.
[39]赵建东,康乐.自动洗碗机的控制系统.国外电子元器件,2004(8): 4~6.
[40]郭强,谢康,姜海明,王浩.电容数字转换器AD7745的工作原理和应用.现代电子技术,2008(14):170~172.
[41]龙海南,张莉莉.AD7745型高精度电容数字转换器.国外电子元器件,2006(8):70~71.
[42] 24-Bit capacitance-to-Digital converter with temperature Sensor AD7745/AD7746.Analog Device, Inc, 2005.
[43] Wuqiang Yang. Key Issues in Designing Capacitance Tomography Sensors. Sensors,2006.