Hermetically sealed high temperature strain gage

Abstract

A hermetically sealed strain gage for measuring strains of high temperature parts comprises an attachment shim plate which is adapted to be secured to the part to be measured. A first inner cylinder member has one end sealingly secured to the shim plate and a second outer cylindrical member is disposed over the first member and has an end which is also sealingly secured to the shim plate. The outer wall of the inner member is spaced from the inner wall of the outer member and first and second spaced apart capacitor plates are arranged at substantially diametrically opposite sides of the inner cylinder member in spaced relationship to each other. A cover plate is sealingly secured to the opposite ends of the inner and outer cylinder members and closes the space between these members. Capacitors are connected electrically outwardly through conductors in a lead wire and the changes of the capacitance caused by the shift in positions of the plates due to the strain provide some indication of the strain involved. Other sensing devices such as photoelectric arrangements may be used to sense the variation in position of the capacitor plates.