An Optical Fiber Grating-based Measurement System with Temperature Compensation

• Main Authors: Wei-Ru Wang, 王唯儒
• Other Authors: Hsing-Cheng Chang
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/14202980385531463253

碩士 === 逢甲大學 === 自動控制工程所 === 99 === The fiber Bragg grating (FBG) measurement system with temperature compensation is developed based on Optoelectronic technology to achieve goals of small, low-cost, high accuracy and portable. The FBG sensors are used to measure weights by checking the center wavelength shift. Long period fiber grating structure senses by demodulating a center wavelength shift of reflected light to sense the energy response due to the physical changes. The temperature compensation is designed by using two FBGs with designing central wavelengths of 1562.76 nm and 1563.06 nm respectively, the reflectivity over 90 %, the full width at half maximum of 0.245 nm and 0.243 nm, one for strain and temperature measurement simultaneously, and the other only for temperature sensing. These two gratings have the same temperature sensitivity and their signal can be subtracted to catch temperature compensation effect. The photo detectors for measuring light intensity are used to convert optical signal into electrical signal. Measured data are analyzed by averaging to compare signal synchronization for reducing transmission delay error. The measured information displays on the LCD and a human-machine interface with data storage to achieve the fiber grating measurement and control as one. Experimental results show that the sensitivity of weight measurements is 6.0 mV/g and the average absolute error 0.46 % in the measurement range of 0 to 70 g. The dynamic temperature compensation sensitivity is 4.9 mV/℃ and the average absolute error 0.51 % in the measurement range of 30 to 60 ℃.