Use of an Optic Lever as a Short Gage Length Extensometer

A short gage length extensometer, based on the principle of an optic lever, was designed and tested as a medium resolution, short gage-length displacement transducer. The goal was to develop a short gage-length extensometer as a potential replacement for foil resistance strain gages. The optic lever used step-index optical fibers to modulate reflected light as a function of target displacement. This provides the basis for a responsive displacement (strain) transducer that is small in size, insensitive to electrical noise, and resistant to elevated temperature and radiation levels. Transducer design was facilitated through use of an analytical model to predict performance. A prototype transducer was tested and compared to foil resistance strain gage results. The prototype demonstrated 25 microstrain resolution over a 10% strain range.