A Planar Coil-Based Novel Two-Channel Differential Inductive Tilt Sensor With a Simple Pendulum Mechanism

This paper presents a novel inductive tilt sensor with a hybrid (planar coil-simple pendulum) architecture. The inductive tilt sensor consists of 2 planar coils, a simple 3D printed pendulum mechanism and a digital read-out circuit. Planar coils are placed under the simple pendulum and a stainless steel sphere is mounted at the end of the pendulum. The distance of the sphere from the coils varies with the tilt angle. Hence, the inductance of the coils is proportional to the inclination. The inductance variation is measured through LC tank circuits containing planar coils. A differential measurement is realized with a micro-controller based read-out circuit designed from scratch using a 2-channel inductance digital converter via LC tanks. This provides a more stable measurement than single-ended measurement. To the author’s knowledge, a 2-channel differential inductive tilt sensor with a hybrid structure consisting of a simple pendulum and planar coils is proposed for the first time in this work. The proposed inductive tilt sensor prototype was tested with a low-cost test setup established in a laboratory environment. Performance tests of the tilt sensor have achieved ±45° operating range, 0.0011 mH standard deviation and 3.89 mH/° sensitivity (%). With the proposed inductive tilt sensor, ± inclination directions can be detected. Furthermore, the repeatability and hysteresis characteristics of the sensor have been evaluated in performance tests. Accordingly, the tilt sensor provides low (0.17%) hysteresis, reasonable operating range and the sensitivity compared to similar-competitive tilt sensors in the literature.