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Displacement sensors play an essential role in many applications. Based on an alternating current magnetic flux measurement, a novel displacement sensing method aimed at developing a practical displacement sensor for ferromagnetic materials is proposed. In this method, the displacement is measured by detecting the magnetic flux in a magnetic circuit, according to a linear relation between the magnetic flux and the reciprocal of displacement. An equivalent magnetic circuit and finite element method are used in analyzing a bridgestructured sensor designed in this paper. Both show that the output of the sensor is linear with the reciprocal of the displacement. A series of experiments have verified the feasibility of the proposed method. The measured results of our prototype sensor show a linear relation with the correlation coefficient R 2 over 0.995 in a measurement range larger than 3 mm. Furthermore, the results significantly indicate that the measured results are not influenced much by the change of ferromagnetic materials with the worstcase error less than 5%.

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As a high-sensitivity magnetic sensor, the magnetic head has been gradually applied to non-destructive testing. Compared with the single coil and the coil with an iron core, the magnetic core can converge the weak leakage magnetic field because it can form a magnetic circuit to transmit the leakage field to the coil wound thereon. So that it has a higher sensitivity. However, in practical applications, it’s found that the pose error of the head affects its sensitivity. Therefore, this paper analyzes the influence of the tilt of the head on the magnetic core’s ability to sense leakage magnetic field, and then the influence is verified by simulations and experiments. The study finds that, when tilted around two horizontal axes, the larger the tilt angle is, the larger the signal is. When tilted around the vertical axis, the larger the tilt angle is, the smaller the signal is.