Design Of Three-dimensional Electrical Resistance Tomography Measuring System

Electrical Resistance Tomography(ERT)technology was adopted to reconstruct image through collecting data information and obtaining the conductivity distribution of sensitivity field.However,research was mainly focusing on 2D space,which lacked the extraction ability of 3D information such as the geometrical shape,relative location and space distribution of dispersed phase.As a result,the 3D ERT system was of great significance to enhance the effect of tomography.The 3D ERT system which can meet the requirements of 3D measurement were designed,and the characteristics were analyzed and experiments were proceeded in this thesis.This thesis was set in the tomography of two phase flow with liquid continuous phase,the design of hardware circuit was the research platform,the 3D ERT system was the research object.The data acquisition and tomography functions were realized,the hardware system was analyzed considering the signal range and sampling precision.The ERT system which can realize the acquisition of 3D data was proposed.The main work of this thesis was showed as follows:(1)The measurement requirements of 3D and 2D ERT system were compared and analyzed,and the modules including frequency and the phase position of excitation signal,instrument amplifier,filter,AD acquisition were designed to meet the demands of the noise ratio and sensitivity combined with the high standard of the speed of data acquisition.(2)The hardware system was finished and with the requirement of the 3D ERT system that each electrode could be chosen as the ground,excitation and detection,the detection mod containing the negative and positive situation.The module was designed with eight pieces 16 MUX 1 CMOS multiplexers.The electrode was given the any of four mode,and satisfied the detection requirement of adjacent,single electrode and diagonal mode,and also can be used in double 16 electrode system.The experiment and theoretical analysis was set for analyzed the influence parameters of the CMOS multiplexers.(3)The Bessel filter was chosen as the main filter module,according to the 3D ERT system huge amount of data acquisition and the high requirement of the acquisition speed.The filter parameters were analyzed with the simulation and the experiment.(4)Considering the same and different layer data were required at the same time,and the amplitude difference of the valid data nearly 100 times.The digital DDS excitation source and the digital amplifier were designed for the change following of phase and amplitude.(5)3D ERT upper monitor software was programmed and contained the data processing and illustrating interface based on Lab VIEW,and the algorithm based on MATLAB.The VISA driving instead of the USB2.0 driving,and the STM algorithm with the dynamic threshold was used in this thesis;(6)3D ERT system was built in laboratory,the production of hardware circuit and programming of software was completed,the parameters characteristics were analyzed.The results of experiments revealed that the circuit board was able to collect the 2D and 3D data accurately.The results of experiments revealed that the system was able to collect the 2D and 3D information of the sensor and imaged the invasive medium which the duty cycle of the section lager than 10%.