Research On Soil Testing Technology Based On EIT

Soil water and salt are important indicators for crop growth and environmental assessment.Most of the traditional methods of soil water and salt measurement can not reflect the spatial distribution of soil water and salt and destroy the soil structure.Electrical impedance tomography(EIT)is a kind of imaging technology aiming at the conductivity distribution of the measured object,which is mainly used in the field of non-destructive testing.Soil Electrical Impedance Tomography(SEIT)based on EIT is proposed to detect soil moisture and salinity.SEIT system is composed of hardware and software.The hardware part generates excitation signal and completes image data acquisition.The software part realizes soil electrical impedance distribution imaging through upper computer.Firstly,this paper analyzes the theoretical basis of EIT imaging,including mathematical modeling,solution of EIT positive and inverse problems.Then,the SEIT system is analyzed and designed,and the overall framework is proposed,which mainly includes the upper computer,the lower computer master station and the lower computer slave station.The master station of the lower computer mainly realizes the communication and data transmission between the upper computer and the slave station of the lower computer,and generates the excitation signal for the slave station of the lower computer.The slave station of the lower computer realizes the functions of multi-channel data acquisition,A/D conversion,multi-channel switch and remote data transmission through the microcontroller.Through the functional analysis,the hardware framework of the lower computer is proposed and the appropriate chip is selected to complete the hardware design.Combined with the design of the hardware circuit,the flow of thecontrol program is proposed.Finally,through the modeling of SEIT system,the positive and negative problems are simulated and analyzed;the hardware circuit and control program are combined to debug the system,which verifies the functions of SEIT system,such as data acquisition,fast switching of multiple switches and data transmission;the performance of the system is analyzed and the image reconstruction experiment is completed,which verifies the rationality of the design of the hardware circuit of SEIT system's lower computer and the correctness of control procedures.