Temperature-Insensitive Inclinometer Based on Transmission Line Fabry–Perot Resonators

This article reports a novel self-compensated inclinometer with a wide dynamic range and high measurement resolution based on two hollow coaxial cable Fabry–Perot resonators (HCC-FPRs). The HCC-FPR is formed between a metal post that shorts the inner conductor and the outer conductor of the HCC and the water level inside the HCC. Changes in tilt angles result in variations of the water level in the HCC, leading to changes in the cavity length of the HCC-FPR. By tracking the shift of the resonance wavelength of the HCC-FPR, a single HCC-FPR can be used as a sensor device for tilt measurements. Furthermore, two HCC-FPRs are used in the inclinometer design presented herein, which enables the inclinometer to achieve self-compensation for variations of environmental factors, e.g., temperature. The tilt measurement sensitivity of the double-HCC-FPR-based inclinometer is also increased. The proposed inclinometer holds several advantages, such as robustness, ease of fabrication, ease of signal interrogation, low cost, and high measurement sensitivity and resolution.