Hardware And Software Design Of Electromagnetic Tomography System

Electromagnetic tomography technology(EMT) is a kind of process tomography technology developed in recent ten years. It combines electromagnetic induction with the mage reconstruction from projection theory.By means of measuring the magnetic field information of the measured space boundary, reconstructing the temporal and spatial distribution’s image of magnetic or conductive materials in space. And the sensor has advantages of non-invasive, non-contact and non damage detection, so it can be applied to industrial process measurement of multiphase flow, chemical separation, foreign body monitoring, geological exploration and Bioelectromagnetics research fields.In order to improve the anti-jamming capability of the experimental system and improve the stability and accuracy of the experimental data, and to realize automatic data acquisition and processing and image reconstruction, building a complete set of electromagnetic tomography system platform. the main research contents are as follows:1、Designing the system circuit of electromagnetic tomography, including the excitation signal circuit which has excellent ability to suppress noise, multi switch circuit, data acquisition amplifier circuit, phase sensitive detection circuit. Firstly, in order to obtain high precision, low distortion sine wave signal, using the DDS chip AD9850 as the excitation source of the system; Secondly, using the reed relay G6K-2P-Y as switch multiplexer switch circuit part, realizing the absolute physical isolation and physical connection control to electrical signal which inputs to coil sensor; thirdly, using precision programmable gain amplifier AD603 as preamplifier of acquisition and amplifying circuit so that it can extract the weak electrical signal which is drowned in the noise; finally, using the multiplier AD534 hardware multiplication demodulation of the signal, so that it can extract a more precise voltage signal than digital demodulation method.2、Building the software platform of electromagnetic tomography system. Firstly, programming STM32 core board on C language to realize logic control to the multiplexer and realizing time accurate A/D acquisition and data processing of 28 groups of DC voltage signal; thirdly, using the VISA module and the MATLAB script node to achieve data reading and image reconstruction.3、Building the experimental platform of electromagnetic tomography system, and running the simulation experiments. The experimental results show that the hardware circuit and software programming on the system realize the display of the detection of weak signal acquisition and amplification, switch control, data transmission and processing, image reconstruction. The experiment result basically reach the expected requirement.