Research On Flux Gate Mechanism And Probe Noise Based On ANSYS

Fluxgate sensor as a magnetic field vector measuring instrument with high measurement accuracy,good stability,easy operation and small size.In actual industrial production,especially geological exploration applications are very extensive.The principle is to use the characteristics of the non-linear periodic change of magnetic permeability of the magnetic material,to use periodically changing alternating magnetic field excitation,fundamentally obey Faraday's law of electromagnetic induction to complete the magnetic field vector measurement of the instrument.At present,its research results are mainly concentrated in foreign countries,and domestic research on fluxgate sensors is relatively lagging behind.This article relies on the funding of the key topic "Long-period distributed magnetotelluric observation system(NO.2014AA06A612)" in the special project of "Deep Mineral Resources Exploration Technology" of the National 863 Program to carry out the analysis of the fluxgate sensor mechanism and the analysis of the impact on output noise.First,the advantages of the dual-core fluxgate sensor are explained based on the fluxgate principle,the working principle of the fluxgate processing circuit is analyzed,and the advantages of the closed-loop fluxgate are pointed out.Combining the arc tangent fitting model of the magnetic material hysteresis loop and Faraday's law of electromagnetic induction,the relationship between the magnetic core parameters in the fluxgate probe and its output induced electromotive force is established.It is also analyzed that the output noise of the fluxgate sensor will increase with the increase in the degree of inconsistency between the number of turns of the excitation coil on the two magnetic cores and the geometric dimensions of the materials of the two magnetic cores.Secondly,according to the JSW dynamic model reflecting the distribution of the Barkhausen effect on the hysteresis loop,it is analyzed that the influence of the Barkhausen effect on the sensor output noise increases with the increase of the excitation magnetic field change rate.Furthermore,it is proposed to use the RLC series excitation method to reduce the excitation magnetic field change rate during the flux gate signal generation stage,so as to reduce the impact of the Barkhausen effect on the output noise.Thirdly,the finite element simulation software was used to simulate the effects of the inconsistency between the number of excitation coil turns,the length of the core material and the cross-section of the core material and the probe output induced electromotive force in the open-loop state.Under the premise of considering the Barkhausen effect,the output noise of the fluxgate sensor using RLC series excitation and RL series excitation in the closed-loop state is compared,and the method for determining the parameters of each original in the RLC series excitation circuit is given.Finally,the conclusions obtained by the mathematical model and finite element simulation are verified through experiments.In terms of the difference in the number of turns of the excitation coil on the two magnetic cores,the simulation and experiment results are consistent,and the difference is within the allowable range of error;In the RLC series excitation noise test,the output noise of the fluxgate sensor can reach 17.6p T/?Hz@1Hz.The experimental results show that the mathematical model and model simulation analysis results are accurate,and the research method is feasible.