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 dielectric liquid capacitive sensing structure. The sensor consists of five electrodes. One electrode serves as the exciting electrode and two pairs of electrodes as sensing electrodes, which are arranged at identical positions surrounding a glass cylinder tube, which is partly filled with dielectric liquid. Based on this unique arrangement, the proposed sensor can detect two components of tilt angle in x-axis and y-axis, 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, which consisted of a 170 kHz sine wave generator, pre-amplifiers, rectifiers, and low pass filters. The experiment results confirmed that the tilt angle sensitivities to x-axis and y-axis are 18.2 mV/° and 58.2 mV/° respectively, with cross-axis sensitivity being less than 5.5% in the linear range. The measured tilt angle resolutions are 0.55° and 0.17° on the x-axis and y-axis respectively.