The Research And Design Of Three-dimensional Five-point Bit Weak Magnetic Field Measurement On Data Acquisition System

In polymer structure materials, there usually exist a certain number of micro defects (inclusions, micro cracks, micro holes, etc.) in process of its synthesis, preparation, machining, storage, transportation and usage. These micro defects will evolve and develop and lead to materials damaged in the external environment and loads.Throughout the damage process, multi-coupling physics fields would present in the fracture process zone at crack tip such as the mass, the stress, the strain, the temperature and the thermomagnet field.The multi-coupling physics field integration tester which aimed for detecting the pyromagnetic effect of high polymer materials with defects is a specialized instrument for this topic researching. It is used for measuring the weak pyromagnetic effect field in the tensile failure process of containing defects high polymer materials. The variation regularity of this weak field has an important significance to study of failure mechanism of high polymer materials.The focus of this project is the "five-point locations three-dimensional weak magnetic field data measurement and acquisition system", containing the design of the sensor subsystem.This paper firstly introduces the background and the significance of project researching, meanwhile elaborates the research status and the development trends of the three-dimensional magnetic field detection technology. And then describes the basic characteristics of the magnetic field detection sensors and the design proposal of three-dimensional five-point locations weak magnetic field data acquisition system.The hardware and software design about it is the emphasis of this paper.To the hardware, the overall design scheme is firstly proposed. And then design of sub-sensor circuit module, hysteresis eliminate circuit module, weak signal amplifier module, analog-to-digital converter module, serial port communication module, single-chip control module are proposed.The HMC2003three-axis magnetic field sensors which produced by Honey well Co. are employed to improve the sensitivity and the stability of system. The AMP04(precision single-supply instrumentation amplifier) is used in system’s weak signal amplifier module amplifier to ensure the precision of requirements. And the STC89C54RD microcontroller is selected in the single-chip control module.To the software, this paper proposes an overall implementation plan of the program. It mainly focuses on the data communication between the host computer and the acquisition system for three-dimensional five-point locations weak magnetic field, such as how to collect the magnetic field data accurately, how to eliminate data errors. And then the host microcontroller data acquisition program has been designed. Finally, the test program main interface of the data acquisition system is introduced. The Lab Windows/CVI software of NI Co. is used as a data collection platform to collect the varying data of magnetic field in a fracture process of polymer structural material specimen.The experimental results indicate that the system has enough sensitivity for a20×10-6GS weak magnetic field. It provides a group of curves containing multi-arguments synchronized with time variation in a polymers PVC sheet test which is stretched with a constant rate and also the variation graphs of the three-dimensional component of the magnetic field.