VIBRATION MONITORING BY USING A DYNAMIC PROXIMITY SENSOR WITH INTERFEROMETRIC ENCODING

An optical sensor for the dynamic measurement of proximity is presente d. The sensor combines an extrinsic geometric transducer with interfer ometric encoding for high vibration sensitivity. Static calibration sh owed a unique variation in interference contrast over at least 60 frin ges, leading to a measurement range of 20 mu m and a resolution of at least 0.033 mu m. Dynamic excitation by using low-amplitude vibrations at 3.6 kHz showed a similar contrast variation, verifying fringe disc rimination up to the sixth order. With verification of dynamic perform ance over all 60 fringes, the sensor should offer a low-cost approach to vibration monitoring in electrical switchgear. (C) 1997 Optical Soc iety of America.