Two-axis tilt angle detection based on dielectric liquid capacitive sensor

This paper presents the design, fabrication and characterization of a two-axis tilt angle sensor based on dielectric liquid capacitive sensing structure. The sensor consists of five electrodes, including one electrode serves as the exciting electrode and two pairs of sensing electrodes arranged at identified positions surrounding a plastic tube, which is partly filled with dielectric liquid. With this unique arrangement, the proposed sensor can detect two components of tilt angle in x-axis and x-axis, simultaneously. A computational multiphysic simulation and experimental measurements study the performance of the sensor. The numerical simulation is carried out with a finite element analysis using COMSOL Multiphysics. A prototype of the sensor was fabricated and its performance was evaluated. The tilt angle sensor is employed on a PCB with conditioning circuit, which consists of a 170 kHz sine wave generator, pre-amplifiers, rectifiers and low pass filters. Experiment results confirmed the performance of the sensor to detect tilt angle in both x-axis and y-axis. Tilt angle sensitivities to x-axis and y-axis are 16.5 mV/degree and 57 mV/degree, respectively, with cross-axis sensitivity less than 5.5% in the linear range.