Research On Combined Capacitance Imaging And AC Synchronous Digital Acquisition System

Process Tomography (PT) techniques, which has been development rapidly in recent several ten years, have made certain progress in field of measurement of two-phase flow/multiphase flow parameter's distribution status. It might become a means for two-phase flow measurement and could be widely applied in industry.Electrical Capacitance Tomography (ECT) is one of the techniques, which is firstly developed for PT. It has low-cost, high-speed, robust and non-intrusive. It has more advantages. So an ECT system of AC measurement combined has studied.1. After analyzing the structure and specialty of capacitance sensor, simulating and calculating the sensor's size. Then construct a new style capacitance sensor with 16 electrodes combined and floated. Its presentation increases the measured capacitances, and benefits for the measured signals and decreases the requirement of data acquisition. 104 projections benefit for improving the quality of imaging reconstruction.2. System's digital circuits are integrated into ispLSI (in system programmable large scale integrated chips) 1032 so as to simplify design and to develop the stability and reliability of the system.3. The ECT system experimental equipment is developed. The system instability is improved by using AC excite and soft compensation in real time.4. In data acquisition system, The application of phase-locked and synchronous detection reduce the cost of the whole system and improve the sensitivity. Carrier signal and modulation signal achieve entirely synchronous too. The utilization of PCL-812PG acquisition card has make the system's developmental time less and improved the system's reliability.5. Visual Basic programmable language is to process, send, and store the data, and then show them out directly.6. By the experimental result and linear back projection (LBP) algorithm to reconstruct the image, and then verify the credibility of the experiment device, realised measuring in time.7. At last, make an evaluation on the system's capability guideline, calculate itssensitivity and linearity by the experimental data, results shows that it has achieved the demand.