Based On Capacitive Digital Conversion Technology Research On The Electrical Capacitance Tomography

Electrical Capacitance Tomography is a new kind of computer imagingtechnology which developed in the1980s.The main pipe is measured by thecapacitance between the electrode surface of the peripheral inside of the object tocalculate the spatial distribution of the dielectric constant, in order to obtain a visualinformation distribution method with cross section, which mainly used for detectingtwo-phase flow within the pipeline industry. Compared with other techniques,two-phase flow visual inspection is a very promising technology for development；therefore， improvement the research and development of ECT technology is arewarding job.This thesis take the key technical issues such as field distribution model ECTsystems, electric characteristics, the sensor electrode structure parameter optimizationdesign, image reconstruction algorithm into account,. The main work is as follows:1.We establish a mathematical model of sensitivity field ECT system which isused as a theoretical basis for the system of other research work.2.By designing the hardware circuit, detected the capacitor pipeline modelinformation and provided the corresponding capacitance data for subsequent imagingwork3.Analysing the "soft field" feature ECT sensitive field, and using finite elementanalysis software ANSYS to simulate the ECT sensitive capacitive sensor field.Through simulation analysis, got the electric force vector distribution and thepotential of the node capacitance sensor equivalent in the cloud distribution,proposing the new positive sensitivity normalized hybrid model to improve theimage quality.4.The study was conducted by ECT system sensitivity of the capacitive sensorsensitivity field distribution, obtained the outside coverage of different electrode and shielding effect of surface electrodes and electrode distance on the capacitancevalue of capacitance tomography systems and sensitive areas, and proposed an arrayof electrodes sensitive design optimization targets, by selecting the appropriatesimulation parameters to optimize the structure and improve the sensitivity fielduniformity and sensitivity, reducing the difficulty of the circuit design to improve thecapacitive sensor design theory.5.For the problem of soft field characteristic of capacitance tomography imagereconstruction, based on the theory of capacitance tomography system principles, bycomparing the results of LBP image reconstruction algorithm, Tikhonov algorithmand improved Landweber algorithm to select the final image reconstructionalgorithm.