Research On High Precision Digital Fluxgate Sensor

The fluxgate sensor is a kind of important equipment to measure the vector magnetic fields.Its working principle is based on the non-linear properties of soft magnetic material.Due to its merits of high sensitivity,good reliability,simple structure and low power dissipation,the fluxgate sensor can be widely used in geological prospecting,navigation and space technology,etc.The traditional fluxgate sensor with analog conditional circuit is easily influenced by the surrounding environment.With the rapid development of computer and information technology,the fluxgate sensor is expected to be miniaturized and digitalized.In China,high precision ground and space-borne fluxgate sensor mainly depends on importation from abroad,which restricts the space and military application of magnetic measurement technology.In this paper,starting with the principle of the fluxgate sensor,a systematic research is conducted on the high precision digital ground and space-borne fluxgate sensor with an attempt to make a breakthrough in the study of magnetic equipment.The main achievements and innovations of this paper are summarized as follows:?1?Established a mathematical model of toroidal core based fluxgate sensor.Utilize the simplified hysteresis curve of soft magnetic material to deduce the relationship between the amplitude of the second harmonic component of induced voltage and the measured magnetic field,and then use it as the theoretical basis for research and development of a high precision digital fluxgate sensor.?2?Developed a new fluxgate sensor architecture which adopts a digital closed-loop feedback mechanism to realize high precision magnetic field measurement.Starting from the structure of the fluxgate probe,optimization of parts including the magnetic cores,coils,framework,shell,etc is conducted.Use a programmable gate array FPGA as the main control chip to perform coordinative control over the excitation circuit,induction circuit,feedback circuit,data acquisition circuit,etc.respectively.The resulted fluxgate sensor achieves a resolution of 0.05nT within the dynamic range of±65000nT.?3?Designed an application specific integrated circuit?ASIC?chip for digital decimation filter which can flexibly adjust output sampling data rate.This chip can completely realize digital signal processing parts including decimating,filtering,etc.,and yield high precision data outputs with different sampling rates.?4?Invented a device that can generate a high precision magnetic field to solve the problem of calibration in a weak magnetic field.This device raises the precision of the magnetic field at the center of an active magnetic field calibration system from±5nT to±0.5nT.?5?Successfully built a high precision digital fluxgate sensor prototype and developed a micro-vibration detection system for XXX satellite attitude and orbit control system?having passed all satellite-borne device testing and certifications,and ready to be launched with a satellite?.The high precision digital fluxgate sensor prototype achieves a dynamic range of±65000nT,a tri-axial linearity of 1.0×10^-5,a noise level of7.393pT·Hz^-1/2@1Hz and a resolution of 0.05nT.The satellite borne micro-vibration detection system based on the high precision digital fluxgate sensor can detect tiny low-frequency vibration less than 0.05°,and totally meet the requirements of the XXX satellite attitude and orbit control system.