Abstract: A strain gage particularly suited for use in detecting and measuring mechanically induced strain in thermally strained specimens including an elongated link, adapted to be fixedly secured to the surface of a specimen, having thermal expansion characteristics matched with those of the specimen, and characterized by a differential capacitor employed for detecting strain induced motion as such motion is effected between the link and the surface of the specimen.

Abstract: An electrical transducer for measuring changes in the size of crack openings. The device is designed to operate at temperatures up to and exceeding 1500.degree. F., is portable, compact, easy to use and reuseable. The device comprises a differential capacitive sensing assembly, arm-like members each including an arm assembly for transmitting the change in crack opening from the crack to the sensing assembly, a flexural pivot to facilitate movement of the arm-like members with changes in the crack opening and means for anchoring the device in the crack. The differential capacitive displacement assembly comprises a plurality of capacitor plates, with the reference excitation plates coupled to one arm assembly and the movable sensing plate coupled to another arm assembly. A bridge circuit couples to the differential capacitive sensing assembly for electrically sensing capacitive variations occasioned by crack opening displacements.