A Rotation Independent In-Place Inclinometer/Tilt Sensor Based on Fiber Bragg Grating

The inclinometer is one of the most important instruments used in geotechnical engineering. The inclinometer is installed into a borehole to monitor the angle of inclination at regular intervals along the borehole to profile the land/soil displacement. In this paper, a novel design of an in-place inclinometer utilizing fiber Bragg grating (FBG) sensor technology is presented. The presented inclinometer is highly sensitive and has an angle measurement resolution of 0.006°. The conventional inclinometers may be twisted involuntarily due to the force that they experience during installation. This twisting may hamper the measurement accuracy of inclinometers. The performance of the proposed FBG-based in-place inclinometer is independent of twisting; hence, its accuracy remains intact even if it is twisted.