Research On Homologous Even Harmonic Fluxgate Magnetic Gradiometer

The magnetic gradient is an important indicator to describe the change of the magnetic field environment in a certain direction,which is the ratio of the two-point magnetic field value to the distance between them.The magnetic gradient has obvious spatial directivity compared to the total field,and has high resolution for magnetic anomalies.The fluxgate magnetic gradiometer assembled by multiple fluxgates is widely used in magnetic gradient measurement in space,aviation,navigation and other fields due to its small size,simple structure,stability and high sensitivity.In the development of the fluxgate magnetic gradiometer,the fluxgate sensor which measure the two-point magnetic field is inconsistent because of the process,and the inconsistency will reduce the accuracy of the gradient calculation result.In order to solve this problem,this paper proposes a homologous fluxgate magnetic gradiometer to improve the consistency of two sensors of the magnetic gradiometer by means of excitation signal homology.In the gradient calculation,the excitation signal error is differentially calculated to improve the accuracy of magnetic gradient.The content of this article is as follows:1.Reconstruct the theoretical output expression of the fluxgate magnetic gradiometer by introducing a frequency error factor,and quantify the expression according to the core specification.Simulating the frequency error influence on the calculation results of the homologous and non-homologous magnetic gradient meters within a certain range.2.The design of the homologous fluxgate magnetic gradiometer sensor probe is according to the homology of the excitation signal.The probe design includes the size of the probe and the excitation,induction,and feedback coil turns.3.The hardware circuit of the homologous fluxgate magnetic gradiometer is designed according to the closed-loop fluxgate circuit design principle.It includes four parts: the excitation circuit,the signal processing circuit,the feedback loop,and the zero reference circuit.4.Comparison experiment with non-homologous fluxgate magnetic gradient meter.The homologous fluxgate magnetic gradiometer measures the same magnetic gradient value with a non-homolog fluxgate gradiometer consisting of two Mag-03 sensors,comparing the measurements of the two magnetic gradiometers.The error of homologous fluxgate magnetic gradient meter is reduced by 53.85%.The experimental results are the same as the simulation results,and the measurement accuracy of the magnetic gradient meter is improved by the homologous mode.