| Two-phase flow system is a complex, nonlinear and dynamic system. It is difficult to measure the parameters of two-phase flow because of interface effect and relative velocity between two phases. Voidage measurement and flow regimes identification technique are two important research fields in the two-phase flow system. The voidage measurement of two-phase flow and the analysis of flow regimes are very important for safety, environment protection, energy conservation and quality assurance in industry. Due to the electrical capacitance tomography (ECT) technology with the advantages of rapid responsive, non-invasion, easy mounting, and process visualization, it is widely applied in study of two-phase flow recently. But ECT technology has the following characteristics: 1) the measured capacitance and its change induced by the measured material concentration variation are very small, but the stray capacitances of co-axial screening cable and CMOS switches are relative very large, so the capacitance detecting is easily affected by the stray capacitances, 2) the electric fields in the sensor's detecting region is affected by the permittivity distribution(flow regimes), non-uniformity of the space responsive sensitivity is very high, and the image reconstruction is undetermined. 3) because the image reconstruction is an ill-posed problem in ECT, the convergence rate is affected by the iterative initial value in iterative image reconstruction, 4) for application in gas/solid two-phase flow, the ECT system online calibration is quite difficult, the factors, as pipe wall abrasion etc. restrict the technology application in pneumatic conveying for long-term continuous process monitoring. Improving the capacitance detecting precision and the quality of reconstructed image is conduced to widening the application domain for ECT technology. The main contributions of this dissertation are as follows:1) In powder weighing feeder system, the average arm of force of measured powder to the fulcrum axis will be unstable due to the shape change of powder heaping in the rotor scale, this will bring high weighing error. The Electrical Capacitance Tomography (ECT) technology can be applied in powder movement monitoring and measurement for visualization research and analysis. A prototype ECT system has been developed which can be operated with single- or two-electrode excitation method and applied for visualizing test and analysis of the DZC-30 with 8 and 12 small spaces respectively. The visualizing analysis of the powder discharge from the rotor scale is redounded to the optimizing design of the numbers of powder conveying spaces and the system control. The re-designed powderweighing feeder systems are applied on practical product line, the results show that the measurement precision is improved and the measurement error is reduced from 3% to 1%.2) The detection of very small capacitance is one of the most difficult problems in developing ECT system because of the very small capacitance, wide dynamic measurement range and large stray capacitance, so the AC-based capacitance detecting method is adopted. In order to improve the signal demodulation precision, the signals for excitation and demodulation are produced by direct digital sine wave synthesizer(DDS) that the phases of the two signals can be set accurately(step =0.1), and the influence of stray capacitance variation is reduced by re-arranging the CMOS switches and their timing.3) Two-electrode excitation method is used for improving the uniformity of capacitance sensitivity. Due to the static electric field in measurement region is a 'soft field', the non-uniformity of capacitance sensitivity is very high, the experiment and calculation show: the uniformity of capacitance sensitivity gets great improvement with two-electrode excitation method compared to single-electrode excitation method, and the quality of the reconstructed image is also improved by the capacitance sensitivity improving and signal enhancing.4) In online iterative image reconstruction, the results by the iterative...
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