A Centimeter-Range Displacement Sensor Based on a Hollow Coaxial Cable Fabry–Perot Resonator

This paper reports a novel hollow coaxial cable Fabry-Perot resonator for centimeter-range displacement measurements. The sensor is fabricated on a novel homemade hollow coaxial cable in which the traditional insulating layer is replaced by air. Two highly reflective reflectors are engineered on this hollow coaxial cable to form a Fabry-Perot resonator in radio frequency domain. The first reflector is fixed, while the second reflector is movable and is permanently connected to a tubular measurement handgrip. The device physics was described. When a displacement is applied to the measurement handgrip, the cavity length of the resonator will change. The change in the cavity length can be determined by tracking the shift in the resonant frequency. The displacement responses and measurement stability of the novel sensor were tested. The experimental results show that the novel hollow coaxial cable-based displacement sensor has a dynamic measurement range of 14 mm with a resolution of 10 μm. The temperature-displacement cross-sensitivity was also investigated. The dynamic range of the Fabry-Perot resonator-based displacement sensor can be easily extended to meter range by employing a meter-long hollow coaxial cable. The reported novel sensor is cost-effective, robust, and easy-tomanufacture, so in situ the sensor can be easily commercialized and has great potential for applications in the construction industry, petroleum industry, and other industries.