Design And Implementation Of Image Data Acquisition System For Electrical Capacitance Tomography

Flow tomographic imaging technology, a recently appeared novel technique, applies Computerized Tomography of medical engineering to multiphase flow measurement. It can measure the parameters of multiphase flow according to the phase distribution image of the cross section of multiphase. Compared with other multiphase flow measurement technologies, it can provide instantaneous microcosmic information of the parts of multiphase flow. Bringing revolutionary change to multiphase flow measurement, it can be widely applied in industry. Because of many advantages, such as low cost, wide scope of application, cheap configuration, non-invasion, safety, and so on, electrical capacitance tomography (ECT) system has become the main trend and the hot focus of tomography. However, a lot of work needs to be done, if this technology comes into practice. The object of this dissertation is on the research of 8-electrode Electrical Capacitance Tomography system. The topics studied are something around data acquisition system for electrical capacitance tomography. The main problems researched in the dissertation and achievements are as follows:The developing situation and the current problems of flow imaging technique are briefly explained with discussing the advantages of electrical capacitance tomography.The principle of the capacitance tomography and some key parameters in individual section are analyzed.A new pattern of integrated electrodes for Electrical Capacitance Tomography is investigated, which describes the design of a custom silicon integrated circuitry to implement a charge-discharge capacitance sensing circuit and optimizes the structure of metrical circuitry. Because ECT has strict demand for capacitance measurement, the design of capacitance/voltage converting circuit which is used to measuring capacitance becomes a nodus. Through studying some kinds of capacitance measurement circuit, a practical one is given. The static characteristic indexes are given in this dissertation after some experiments have been done. ASIC & electronic components are selected according to the demand of the system, and writing data acquisition software which can drive and control the entire circuit.With image reconstruction, experimental results illustrate that the system is promising. Also, the error of image reconstruction and the error of concentration measurement are less than 2.5%. A kind of high speed means of communication is discussed, which adopts the method of combining USB with RS-485 interfaces, and can improve remote telecommunication capability of data acquisition system.In order to improve real-time quality, practicality, expansibility of data acquisition system, embedded system programming is introduced, which changes the traditional pattern of programming on singlechip. Some meaning tasks have been done, such as pruning and transplanting embedded real-time operation system kernel. Embedded system exploitation is discussed, linking with software engineering and proposing the mode facing different hardware through adding up Hardware Abstraction Layer.