IN this paper, a novel compact strain sensor using grating diffraction method this method is presented. The grating generally with a frequency of 1200 lines/mm attached on the surface of a specimen is illuminated by a focused laser beam. The centroids of diffracted beam spots from the gratin is automatically determined with two position-sensitive detector (PSD) sensors connected to a personal computer. The shift of diffracted beam spots due to the specimen deformation is then detected. The influences of noise sources and system geometry on system performances, such as sensitivity, spatial resolution, strain range and measurement linearity are discussed. Strain sensitivity of 1 micro-strain can be achieved. The spatial resolution, for strain measurement of 0.4 mm is attainable. The system can be used for continuous measurement and for both static and dynamic test.
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