Design Of Data Acquisition System In 12-Electrode ECT And Software Development

Electrical capacitance tomography technique (ECT) is a kind of process tomography technique (PT) based on the sensitive principle of capacitance. The technique with its advantages such as no radiation, no invasion, high speed of response, simple structure, low cost, wide application range, better safety and so on has now being a most important technique of two-phase flow parameter measurement. But there is still a lot of work to be done for practical use of the technique, for example: low capacitance measuring, improving the anti-interference ability and so on.This dissertation is based on the study of 12-electrode electrical capacitance tomography system for oil-water two-phase measurement. The characteristics, the operation principles, and the structure of ECT system are studied. Low capacitance measurement circuit is designed according to the data from finite element analysis. Phase sensitivity demodulation is used in the system for restricting noise interference. The influence of coupling capacitance to the measurement system is analyzed. A model of coupling capacitance compensation is proposed, and is built using hardwire and software of real time compensation. A circuit of electrode-chosen is designed, and electrodes share the C/V converting circuit and signal generator. The feasibility and rationality of using RS232 are analyzed, and digital signal processor chip is taken as core controlling chip. The software of upper and lower is programmed. Finally, experiment is done in the data acquisition system. The results of the experiment prove that the method is feasible, and the sensitivity of the system is 0.49974V/pF. The method solves the precision problem of low capacitance measurement, enhances the anti-interference ability of the system.