An integrated Dual-Parameter sensor based on FBG for Temperature/Pressure monitoring of fluid pipeline

Abstract

This article proposed an integrated temperature/pressure dual-parameter sensor in small hydraulic pipelines, and a set of small hydraulic pipeline experimental system is specially built to verify the dynamic measuring performance of it. A fiber Bragg grating (FBG) integrated sensing structure was designed and fabricated to achieve simultaneous monitoring of temperature and pressure. Specifically, the temperature measurement structure was encapsulated by an Invar capillary and a stainless-steel protective tube with asymmetric holes on both sides. The protective tube blocked the impact of the fluid on the temperature sensing element. Asymmetric holes ensured that the hydraulic oil filled the protective tube, allowing a uniform temperature field to surround the temperature sensing element. The secret to achieving large-scale temperature measurement was the Invar capillary’s low thermal expansion coefficient. The pressure measurement structure was made of beryllium bronze diaphragm and FBG. The strain captured by FBG was converted from fluid pressure by a beryllium bronze diaphragm. High sensitivity and simplicity were significant advantages of this pressure measurement structure. The close installation position of the two modules effectively ensured the temperature compensation effect of the pressure measuring module. The results indicated that the integrated dual-parameter sensing structure worked efficiently in the temperature range of 30–80 ℃ and the pressure range of 0–1 MPa, which was widely adopted in small hydraulic pipelines. The temperature and pressure sensitivities were 12.055 pm/℃ and 3.643 pm/kPa, respectively. The FBG temperature/pressure dual-parameter integrated sensor proposed in this article achieved effective monitoring of temperature/pressure parameters in small hydraulic pipelines.