Nano-copper suspension filling based fabrication and application of FBG temperature sensor with fast response function

The fast response is a significant index for measuring the performance of temperature sensors. In this paper, a copper capillary temperature sensor is developed utilizing fiber Bragg grating (FBG) as the sensing element and nano-copper suspension as the filler. Nano-copper suspension with high thermal conductivity is meaningful to improve the response speed of this sensor. The relationship between the preparation parameters of nano-copper suspension and the thermal conductivity is accurately established to obtain the optimum response time of the temperature sensor. The suspension with small particle size and high concentration significantly improves the sensor's response speed, which is close to the bare FBG. In addition, the temperature sensor encapsulated with a copper capillary tube has high sensitivity, which is three times that of the bare FBG. This temperature sensor and bare FBG are simultaneously applied to the motor with a winding inter-turn short circuit as the initial fault. Both this sensor and the bare FBG capture the coincident temperature field, which implies that the sensor has no apparent response lag compared with the bare FBG in practical applications. Results demonstrated here may afford some valuable references for obtaining temperature filed in small electromechanical components.