Development And Performance Research Of Fluorinated Polyimides Coated Fiber Bragg Grating Humidity Sensor

At present, the building energy efficiency has received much attention of the wholesociety. The heat transfer of the building envelope is the main source of building energyconsumption. Temperature, humidity and the relative sliding at surface of wall materialsand insulation materials affect wall insulation performance, but the humidity sensorfailed to accomplish the task of monitoring the humidity of wall, so the dinvention of ahumidity sensor for the wall and wall insulation performance monitoring system isnecessary.The paper first discusses the fiber grating sensing principle, the sense of wetprinciple of the fluorine-containing polyimide and the humidity measurement theory offluorinated polyimide coated fiber grating, a fluorine-containing polyimide coatedfibergrating production process, and then reseaches the package of fiber gratinghumidity sensor, and then researches the effect of fluorinated polyimide curing processto the humidity and temperature sensitivity coefficient of fiber grating humiditysensor, and then determines the humidity and temperature sensitivity coefficient of fibergrating humidity sensor, the center wavelength of the fiber grating humidity sensor atspecific temperature and humidity, and then reaserches the humidity sensing propertiesof fiber grating humidity sensor-the sensor range, the reading accuracy, error analysis,response time, hysteresis, waterand long-term stability, and then reaserches the effect offluorinated polyimide curing process to the sensor humidity sensing properties, and thenreaserches the part which the insulation performance monitoring system of building’sexterior wall should have, and then reaserches the layout of the sensor in the wall andthe evaluation method of wall insulation performance.The final results of this paper are: the invention of fiber bragg grating humiditysensor for the wall, and on this basis, building a wall insulation performance monitoringsystem. The sense of wet components of the humidity sensor invented is fluorine-containing polyimide-coated fiber bragg grating, which can measure the humidity fromn5.7%rh to97.3%rh.Its reading accuracy is0.1%rh and the measurement error is about4.5%rh.The sensor’s response time is about45min and the maximum hysteresis is1.8%rh.The water resistance and long-term stability is good. The monitoring systemconsideres the impact of the temperature, humidity and the relative slip at the surface ofwall materials and thermal insulation materials to wall insulation performance. It canconstantly monitor the temperature, humidity and strain of the key parts of the buildingwall, and can use the collected data to simulate the temperature, humidity and strain ofthe wall, and can make the wall insulation performance evaluation.The developed fiber bragg grating humidity sensor can be buried in the wall, andmonitor the internal humidity of the wall. Wall insulation performance monitoringsystem can make more reasonable assessment to the insulation properties of the wall, provide a theoretical basis and technical support for energy-saving design of theconstruction, construction quality control and maintenance methods of the external wall.