A Robust Two-axis Tilt Angle Sensor Based on Air/Liquid Two-phase Dielectric Capacitive Sensing Structure

Abstract

This paper presents the design, fabrication, and characterization of a two-axis tilt angle sensor based on the air/liquid two-phase dielectric capacitive sensing structure. The sensor consists of five electrodes, one serves as the exciting electrode and two pairs of electrodes as sensing ones, which are arranged at identical positions surrounding a glass cylinder tube. The glass cylinder tube is partly filled with dielectric liquid to form the air/liquid two-phase dielectric medium. Based on this arrangement, the proposed sensor can detect roll and pitch angles, simultaneously. A computational simulation and experimental measurements are performed to study the performance of the sensor. The numerical simulation is carried out with a finite element analysis using COMSOL. A prototype of the sensor was fabricated, and its performance was evaluated. The tilt angle sensor was employed on a printed circuit board with a conditioning circuit, consisting of a sine wave generator, pre-amplifiers, rectifiers, and low pass filters. The experiment results confirmed that the roll angle detection has a linear range in the range of −60° to +60° with non-linearity error of 6.6%. The sensitivity and resolution in this range are 18.2 mV/° and 0.55°, respectively. For pitch angle detection, the linear range is −16° to +16° with non-linearity of 10%, and sensitivity and resolution of 58.2 mV/° and 0.17°, respectively.