| As a kind of nondestructive and visible measurement technique, since its low cost,fast response, harmless and non-invasive, electrical capacitance tomography is appliedin many industrials. This thesis has done plentiful study on design of capacitance sensorin ECT system. The main research work and results are explained as follows:1. A mathematical modeling of capacitive fringe effect under the special conditionsis analyzed based on the operation principle of capacitive sensor. The experimental re-sults indicate that the key parameters in sensor design will affect the sensor performancegreatly.2. The evaluation standards of capacitive sensor performance are supplied. Theperformance of the designed proximity capacitive sensor includes penetration depth,signal strength, sensitivity of the measurements and reconstruction imaging resolution.The sensor measurement performances are quantitative analyzed.3. By using finite element method (FEM),3D modeling of designed capacitivesensors is built. The influence of earthed outer screen, axial driven guards, axial earthedend guards and radial earthed guards on sensor performance is discussed and analyzed.The reconstruction imaging test by using optimized sensor with proper imaging algo-rithms indicates satisfied results.4. Aiming at the deficiency of flexibility and the requirement of tomography duringthe process of measuring the traditional ECT sensor, a new adaptive ECT sensor is pro-posed. This new adaptive ECT sensor can be composed of plate array combinations inorder to realize the purposes of using varied modes in measuring. By explaining thestructure of this new adaptive ECT sensor and its work mode in detail, according to thesimulation results of these two work modes, the structure of this new adaptive ECTsensor not only meets the requirements of sensibility and resolution but also has a goodflexibility, which can replace the traditional structure and become a new research direc-tion of sensor design. |
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