Compact Magnetic Gradiometer and its Astatization

Abstract We present a compact (10-cm head size, 3-cm base) axial magnetic gradiometer with a method of its astatization (i.e. suppression of false response to homogeneous field). For astatization, we use two integrated orthogonal sensors and a second-order polynomial correction; after astatization the gradiometer error is suppressed more than 1000×. The gradiometer has been successfully used in a real-world metal-detection task which was allowed by the low gradiometer astatization error of ± 50 nT/m and its noise of 1 nT/(m√Hz) @ 1 Hz.