Development of a mirror mounted fiber optic inclinometer

A fiber optic inclinometer enables long distance transmission in hazardous environments without signal loss. This paper presents a wide measurement range fiber optic inclinometer for a stable sensing principle and simple sensor structure, which were realized using a single transmissive grating panel, reflective mirror, and optical fibers as transceivers. In comparison with the conventional transmission type fiber optic inclinometer design, the proposed scheme's cable design was simplified by 50%. The variation curve of the gravity-referenced static acceleration, measured using the proposed fiber optic inclinometer, was sinusoidal and it was compared with actual gravitational acceleration. The developed inclinometer featured nonlinear sensitivities of 1.97°/rad (90–75°), 2.19°/rad (75–60°), 2.49°/rad (60–45°), 3.23°/rad (45–30°), 5.84°/rad (30–15°), and 10.42°/rad (15–0°) according to the measurement range. The maximum absolute error, which was analyzed at 5° intervals, was 0.96° in the full scale measurement range (−90° to 90°). In the full scale range, the R-square value was 0.9999 between the measured and actual tilt angles based on linear regression analysis, and it demonstrated good agreement.