A New Calibration Method Of Fluxgate Magnetometer Based On Zero Magnetic Device

Three-axis fluxgate magnetometers are widely used in space exploration,positioning navigation,geological exploration and other fields.As high-precision vector magnetometers,their accuracy will directly determine the accuracy of the obtained magnetic field data.However,there are three kinds of self error in three-axis fluxgate magnetometers because of limited by the machining precision and the characteristics of electronic circuit itself,such as zero shift error,proportional coefficient error and non orthogonal error.These three kinds of errors will cause the readings of fluxgate to deviate from the real magnetic field values.Therefore,the error parameters need to be calibrated before the actual measurement.Although the traditional scalar calibration method is widely applied,there are still many problems.For example,the background magnetic field with large magnetic noise,the magnetic interference of the non-magnetic rotating platform,the high uniformity of the magnetic environment and the low efficiency of the experiment.These problems limit the further improvement of calibration accuracy.In view of the above problems,and combined with the zero magnetic device,a new calibration method of controllable standard magnetic source based on zero magnetic device is proposed in this paper.The new method starts from reducing the noise of magnetic field to improve the calibration accuracy,and uses the low magnetic field noise environment inside the zero magnetic device.By calibrating the error parameters of the three axis uniform field coil in the zero magnetic device,a controllable standard magnetic source is formed by the zero magnetic device and the calibrated three axis coil,and a large number of different direction space vector magnetic fields can be produced to calibrate the fluxgate sensor.In this paper,the new calibration method is divided into two steps,“the calibration of three-axis coil based on zero magnetic device” and “the calibration of three-axis fluxgate magnetometers based on controllable standard magnetic source”.In view of the “three-axis coil calibration based on zero magnetic device”,by analyzing the existing calibration methods of three-axis coils,the traditional calibration model is optimized.The three error parameters of the three components of the environmental magnetic field are introduced to construct the error model containing 9 error parameters.In view of the “three-axis fluxgate calibration based on controllable standard magnetic source”,an error model with 9 error parameters including 3 kinds of errors is constructed.And the specific process of the new calibration method is summarized.Two specific problems of the new calibration method,namely,“the coupling of the shielding layer and the external magnetic field of the three-axis coil” and “the position deviation of the vector and scalar magnetometers”,are analyzed with the help of COMSOL and MATLAB software.Considering the zero magnetic device of this paper,a three-axis Helmholtz coil with a diameter of 0.46 m is selected as the magnetic field device,and the two problems are solved reasonably.With the help of MATLAB software,the calibration process of the new calibration method is simulated and analyzed based on the measured data of the internal magnetic field of the zero magnetic device.With the help of the idea of probability and statistics,the influence of the input current situation on the calibration results of the two steps of the new calibration method is analyzed,and the optimal input current situation of the two steps is clarified.Then the simulation and comparison of new calibration method and traditional scalar calibration method,which proves the advantages of new calibration method.At last,the experimental platform is built according to the existing resources.and the new calibration method is used to calibrate the 9 error paramaters of Mag-03 fluxgate sensor.The feasibility of the new calibration method is proved through the analysis of data and calibration results.