Design Of Medium-high Frequency Alternating Magnetic Field Measurement System

With the rapid development of science,technology and industry,the alternating magnetic field is more widely used in many fields,such as military,medicine,nondestructive detection,food preservation and so on.Measurement methods and related instruments of magnetic field have been also rapidly developed,but the measurement of MHF(medium and high frequency)alternating magnetic field is still a problem at present.This thesis comes from the measurement and control requirements of MHF alternating magnetic field used for sterilization and preservation in food industry.At present,the measurement of three-dimensional MHF alternating magnetic field is mainly focused on low frequency strong magnetic field and high frequency weak"magnetic field,but there are still three problems:high frequency,strong magnetic flux and point measurement.Therefore,a three-dimensional probe is designed and a MHF alternating magnetic field measurement system based on FPGA and ARM is proposed in this thesis.Firstly,the measuring method of the three-dimensional MHF alternating strong magnetic field and its research status at home and abroad is introduced in this thesis.At the same time,the generating principle of alternating magnetic field and the characterristics of measured magnetic field are analyzed.After comparing and analyzing the main methods of measuring alternating magnetic field,the electromagnetic induction method is used to measure the alternating magnetic field,and the system measurement method based on FPGA and ARM is proposed.A hardware circuit system is designed,which is suitable for measuring the alternating magnetic field.As the measuring requirements,a spherical probe coil is made and the minimum circuit system of FPGA is designed.Synchronous measurement of three components of field strength at every measuring spot is achieved by combining amplitude-limiting circuits,programmable amplifiers,DC bias circuits,high speed AD and other peripheral circuits.S3C6410 ARM chip is selected as the host processor and the communication interface circuit between the ARM development board and FPGA is implemented.According to the characteristics of FPGA and ARM processor,the task allocation and system software design are completed.For FPGA software design,QARUTUS ? 13.0 software is adopted.The internal function modules of FPGA are realized with the hierarchical design mind,which include dual port RAM cache module,precision frequency measurement module,spectrum transform module,the ratio correction module,serial communication and other algorithms modules.In the section of ARM software design,WinCE kernel operating system is customized and ARM application software development by NI-LabVIEW Touch Panel module is finished.Application software mainly includes serial communication module,data analysis and processing module,waveform display module,file storage module and others.Finally,system debugging is completed and experimental system is built,the experiment results illustrate that the measuring method of three-dimensional MHF alternating magnetic field has higher detection accuracy and stability.Meanwhile,the measurement system can be used as a portable instrument.