Calibration Of The F-P Strain Sensor And Investigation Of Installing Technology

As a new strain sensor, Extrinsic Fabry-Perot interferometer (EFPI) strain sensor was widely utilized in health monitoring of large civil infrastructure. To fit the harsh installation condition of civil engineering application and ensure the installing- livability, it necessary to wrap a metal shell around bared EFPI. Therefore, the deformation of structure does not load on EFPI directly. The mechanical transferring character of mentioned metal shell reduces the sensitivity of EFPI strain sensor, and even more, it does harm to sensor's reliability and precision. So it very important to study the calibration technique of EFPI strain sensor.In this thesis, the overview of EFPI sensing technology was simply introduced firstly. Then the calibrating necessity of EFPI strain sensing probe was analyzed and the study content of the paper was put forwarded. Both calibrating systems corresponding to embedded and surface-attached EFPI strain sensing probe was studied in detail, and the data processing software were also introduced. Before using in calibrating-work, the accuracy of some instruments, such as grating micro-displacement sensor, fiber strain gauge and resistance strain gauge, were verified. The grating micro-displacement sensor was also sent to technical supervision bureau for an accuracy certification. All calibrating data was carefully analyzed, and precision of each kind of sensing probe was evaluated. The reasons of measuring-error in these two calibrating systems were discussed. The data indicated that, different installing- technics would lead to different calibrating results, i.e., the sensing probe with poor installing condition has coarseness accuracy than probe which has been installed correctly. Whereupon, extra study on installing- technics of EFPI sensing probe were carried on. The research demonstrated that, the frame of our embedded sensing probe is well designed and it is suitable for embedding in concrete structure before pouring, but the toughness of our surface-attached EFPI sensing probe was too hard to be attached by common epoxy. It should be weld on metal structure of fixed on concrete structure by expansile-bolt. Finally, some improvement advice on both calibrating system and sensing probe itself were put forwarded according research results mentioned above.