The Study Of Weak Magnetic Field Detection Technology Base On Fluxgate Sensor

Fluxgate magnetometer is a kind of weak magnetic field detection device, it is base onnon-linear characteristics of the soft magnetic material when the material is magneticsaturation. Fluxgate technology began in the nineteen thirties, with the development ofscience and technology, the fluxgate technology is widely used in geophysics, aerospaceengineering, biomedicine, military field, material nondestructive flaw detection and otherfields. For high resolution, high stability and other advantages, fluxgate sensor has greatadvantages in the weak magnetic field detection, it is the ideal equipment for measuringweak magnetic field.This paper studies the fluxgate sensor principle，establishes and analyses mathematic-al model of the fluxgate sensor, obtain the influence factors of fluxgate output signal;design and make fluxgate sensor with high magnetic permeability material-cobalt baseamorphous alloys VITROVAC6025Z as core material; DDS （direct frequencysynthesizer） excitation circuit is consists of MCU and AD9850; after being poweramplification, the drive signal can be use to drive excitation coil, makes the magnetic coresaturation; the part of signal detection is consist of PCI-1716data acquisition card and theLABVIEW development environment. The weak magnetic fields measurement system isconsist of above components, it is a virtual instrument. Signal acquisition by dataacquisition card, data processing is in LABVIEW, make some appropriate changes on thepulse amplitude method, extract two and four harmonics from the even harmonics that canmark the magnetic field intensity, after processed, the magnitude of the magnetic field ismeasured.Use FG708S function signal generator to provide encouragement in experiment, theparameters of excitation signal can be selected convenience, after contrast experiments, thesensitivity of the system is higher as the amplitude of sine excitation is5V, the frequencyis10kHz. Use Tesla for fluxgate magnetometer calibration in a steady magnetic field,experimental results show that the fluxgate magnetometer has good linearity, sensitivity to1.783mV/uT, resolution of uT. The fluxgate magnetometer realize environment zerocalibration in different magnetic fields, the measurement for weak magnetic field is more accurate. The system base on virtual instrument has simple structure, easy to maintain, andhas practical value in a certain way.