Hermetically sealed strain gauges for measuring strains of high temperature parts

摘要

A hermetically sealed strain gauge for measuring strains of high temperature parts comprises an attachment shim plate (12) which is secured to the part to be measured. A first inner cylinder member (14) has one end (14a) sealingly secured to the shim plate (12) and a second outer cylindrical member (16) is disposed over the inner member and has an end (16a) which is also sealingly secured to the shim plate (12). The outer wall of the inner member (14) is spaced from the inner wall of the outer member (16), and first and second spaced apart capacitor plates (18 and 20) are arranged at substantially diametrically opposite sides of the inner cylinder member (14) in spaced relationship to each other. A cover plate (24) is sealingly secured to the opposite ends of the inner and outer cylinder members (14 and 16) and closes the space between these members. The capacitor plates (18 and 20) are connected electrically to the outside of the outer member (16) through conductors in a lead wire (22), 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 means such as photoelectric arrangements (26 and 28) may be used to sense the variation in position of the capacitor plates (18 and 20).