Design and Development of a New Non-Contact Inductive Displacement Sensor.

A new, non-contact, planar spiral coil-based inductive displacement sensor is presented in this paper. The proposed sensor employs a fixed planar coil and a movable $U$ -shaped magnetic core. The sensor is designed such a way that the shape of inductance versus displacement x$ is sinusoidal. Due to this feature, the value of x$ is obtained easily from the inductance measured without the need of a look-up table, which is not the case for most of the planar coil-based sensors. The proposed sensor has very low sensitivity to vertical misalignment of the core. A phase-sensitive detector-based measurement scheme is employed to measure the inductance. The inductance characteristic of the proposed sensor is symmetric with respect to the center of the coil. A simple capacitive detection scheme to distinguish the position of the core between the two halves of the coil is proposed in this paper. This method enables to extend the sensor range with multiple coils connected in series. A prototype of the proposed sensor has been developed and tested. The sensor has a worst case error of 0.6%. A modified sensor using two coil sets has been developed. The modified sensor has high sensitivity over its entire range, unlike the first prototype. It has a worst case error of 0.2% and a resolution of 6.5 . The low-cost sensor developed will be useful for many industrial linear position sensing applications. [ABSTRACT FROM PUBLISHER]