Vector Magnetic Gradiometer with Adjustable Gradient Sensitivity Based on Anisotropic Magnetoresistance

Abstract

In this study, an anisotropic magnetoresistance (AMR) vector magnetic gradiometer with adjustable gradient sensitivity was developed to measure the magnitude of the vector magnetic field gradient. First, two AMR chip sensors were used to construct the measurement probe of the magnetic gradiometer, and a signal-conditioning circuit based on proportional integral closedloop control was designed to create a vector magnetic gradiometer with adjustable gradient sensitivity. Next, by using the circuit diagram of the AMR vector magnetic gradiometer, the measurement principle of the AMR vector magnetic gradiometer was theoretically studied, the relationship between the magnetic field gradient and the output voltage of the AMR vector magnetic gradiometer was obtained, and the noise of the AMR vector magnetic gradiometer was analyzed. Finally, a gradient test platform was constructed to test the magnetic field gradient measurement performance of the AMR vector magnetic gradiometer. The experimental results revealed that when the feedback resistance of the V/I conversion circuit of the AMR vector magnetic gradiometer is 200 Ω, the noise level is 122.36 pT/Hz 1/2 at 1 Hz, and the nonlinearity and gradient sensitivity are 0.9968% and 11.707 μV/(nT/m), respectively. The proposed gradiometer can be used to measure the gradient of the input magnetic field, and its interesting application is the gradiometer to measure magnetic field anomalies in the presence of large uniform magnetic field disturbances.