Research On Transducer And Data Acquisition System For 12-Electrode ECT

Two-phase flow has a wide range of application in industry.The research on two-phase flow is developing rapidly. The subject on two-phase flow has been one of the frontier subjects concerned deeply in the world. The measurement of two-phase flow is difficult, owing to the complexity of the characteristic of two-phase flow. In many cases, the two-phase flow measurement technique has been one of the factors that bottleneck the study in the field of two-phase flow.Electrical capacitance tomography (ECT) is a kind of process tomography techniques that are widely studied. ECT is fast, non-invasive, low cost, safe and widely applicable. It has become one of important techniques for two-phase flow parameter measurement. But there are some problems and difficulties in ECT designs and ECT applications, for example: low capacitance measuring, improving the anti-interference ability and so on.This dissertation goes into research of ECT key technique in its hardware designing, experiment devices based on 12-electrode ECT system have been designed and data can be transmitted between upper computer and lower computer .The main contribution and results are as follows:1. The basic principle and characteristics of PT are compared.The characteristics, basic principle,and system structure of ECT are discussed.2. The architecture of array of sensing electrode has been designed ,all the electrodes use the same excitation source and C/V converting circuit.This system facilitates the investigating of different measurement plans.3. An AC based C/V converting circuit is developed,which has antijamming ability for the stray capacitance, high resolution and low drift.and it has been proved by experiments that the circuit has good characteristics and is applied in the ECT system.4. The influence of stray capacitance and its change on the C/V circuit is discussed, and it can be concluded that the influence of stray capacitance and its change is very little comparing to that of the excitation signal.5. The effect of CMOS switch coupling capacitance to the system instability is compensated by a software approach in real time.6. A DSP based data acquiring system has been developed, which can advance the speed of data acquisition and processing, also communicate with upper computer expediently and fleetly in real time after analyzing the feasibility and rationality of using RS232.