Tuber Electrical Resistance Tomography Data Acquisition System Based On FPGA

Electrical Resistance Tomography(ERT)is an important branch of Electrical Process Tomography(EPT).It is mainly applied to oil field and chemical industry,in advantages of no radiation,quick speed,simple structure,and high cost performance.The concept of Tuber Electrical Resistance Tomography(TERT),which raised by our group,aims to utilize ERT tech to monitor the growth state of plant tuber in a no radiation and visual way.It also provide a general utility tool for new variety breeding in Precision agriculture and Electronic agriculture.The 6 layers' electrodes array,each layer concludes 16 electrodes,had been designed in the article,based on the former research in the finite element analysis of the sensor system.There are two factors in the TERT data acquisition system,which is different from the ERT system.First is that the difference between the medium,the medium of TERT system is soil,which has a bigger and uneven resistance distribution.Second is the data acquisition system take more important in the imaging resolution and image quality rather than the imaging speed,which traditional ERT system mostly take care of.The main work of this article is as follows:(1)Design and accomplish the TERT sensitive electrode array subsystem,based on the impedance model analysis and simulation of TERT system.(2)Accomplish resistance tests,by using the TERT sensitive electrode array subsystem we built.These tests verify the feasibility of TERT theory,and provide basses of data accomplish system design.(3)Design and accomplish the TERT data acquisition system.The system's main control chips are FPGA and ARM.And it can realize a data acquisition task of a 6 layers electrodes array,each layer has 16 electrodes,in an adjacent injection/measurement mode.(4)Accomplish the software for the FPGA program by using Verilog language,and ARM program in C language.The software provide functions such as:switch array control,data acquisition,digital filter,communication with the computer,etc.(5)Conduct a series of experiences,using the data acquisition system,to verify the theory of TERT,and modify the data acquisition system.Finally,the image reconstruction of tuber in the soil was succeeded,by using the TERT measurement data.The hardware in this system includes:TERT sensitive electrode array subsystem,constant current source,onepiece of signal disposal circuit board,one piece of central control board,six pieces of switch array control board.And we also conducted soil resistance test and performance test experience of data acquisition system during the design process.The system can realize a tuber's boundary voltage acquire and image reconstruction,which the tuber's size should be bigger than 1.21 cm2 on each plane.