Design For Three-Dimensional Electrical Resistance Tomography (ERT) Hardware System

Electrical resistance tomography (ERT), a technology simplified from electrical impedance tomography, is a significant branch of process tomography technology. With its nonradioactive and online characteristic, the ERT system is deemed to be an important method in the field of two phase flow measurement and is widely used in industry processes, especially in steel industry.ERT systems are studied based on two-dimensional models in most of the present analyses. The conductivity distribution was reconstructed based on a section of the sensitivity field. However, in consideration of the complicated multiphase flow process, three-dimensional information of the materials’ characteristics in the sensitivity field is needed. Since the three-dimensional information could not be obtained from two-dimensional system, a three-dimensional ERT system is needed to reconstruct the sensitivity field.The working principle, background, as well as the realizing way of the ERT technology was studied in this thesis. A three-dimensional ERT hardware system was built based on the ERT system. Sensor system, hardware circuit, and host computer system were designed. The main work of this thesis is showed as follows,(1) Related literatures of ERT system were studied in this thesis; the influences of the electrodes’ material, electrodes’scale, electrodes’ combination, incentive method, and sampling method on the ERT system were analyzed. Based on the analyses, a 3-layer 8-electrode sensor structure, which was capable to measure three-dimensional information, was proposed in this thesis.(2) The two working mode of ERT system, voltage excitation and current excitation, were analyzed; in consideration of the structure characteristics of ERT sensors, the current excitation was used in this thesis.(3) Based on previous experiments, a three-dimensional ERT hardware system based on LPC2148 microcomputer was designed; excitation signal creation module, data acquisition module, and channel selection module were designed.(4) With the sensor structure and working mode designed in this thesis, a section switch module and a channel selection module based on analog switch chip MAX307 were proposed.(5) Software of the host computer and the lower computer were programmed; programs of the chip AD9833, the instrumentation amplifier, and the analog switch chip MAX307 were included in the lower computer programs; the experiment interface of the host computer software was developed based on VB. The lower computer was ordered by the host computer; the data transferred from the lower computer was analyzed in the host computer and displayed on the experiment platform.(6) An experimental hardware platform based on ERT system was built and the stability of the system was analyzed. Results of the experiments showed that the platform could work stably for a long time. The whole system and the data obtained in the system were tested. Results of the experiments showed that the system in this thesis accorded with the design goals. The errors of the system were analyzed; improvement suggestions were proposed based on the error analysis.