Hardwre Design Based On DSP And Software Development For Electrical Capacitance Tomography System

Electrical capacitance tomography technique (ECT) is a widely studied technique for the measurement of two-phase flow parameters.Owing to the advantages of low-cost,high-speed capability,non-invasion,wide applications and reliability,ECT has been applied in many fields.However,it is still in the stage of laboratory research due to a few problems and difficulties.This dissertation is based on the study of electrical capacitance tomography system for oil-water two-phase measurement based on DSP(digital signal processor). The key section of the system is the low capacitance measurement circuit. The methods and principles of the low capacitance measurement circuit are analyzed in detail.The low capacitance measurement circuit is also analyzed in detail. The technique crux is the value of the detected capacitance signal well below the coupling capacitance signal and stray capacitance signal.The circuit of alternating current capacitance measurement and the technology of phase sensitivity demodulation are adopted to solve the technique crux. The solution has the advantages of the characteristics of the low drift, the high signal to noise ratio, the short duration of the circuit building. A DSP based data acquiring system has been developed, which can communicate with upper computer expediently and fleetly in real time, also advance the speed of data acquisition and processing.The upper and lower software is designed. The major functions of the software include real time compensation, the controlment of the system, communication between the upper and lower.The main problems researched in the dissertation and achievements are as follows: The important meaning of multiphase flow measurement to the science research and industry production is briefly explained.The current status and developing trend of the future process tomography is analyzed.The 12-electrode capacitance transducer is designed based on the influence of structure parameters and design ruler. Phase sensitivity demodulation is used in the system for restricting noise interference. A model of coupling capacitance compensation is proposed, and is built using hardware and software of real time compensation.A DSP based data acquiring system has been developed. The experimental results show that the method is practicable to the measurement of small capacitance.