Patent ID: 8096191

Claim:
An apparatus for measuring strain in a test specimen comprising: an upper bolt and a lower bolt for mounting said test specimen; a first ring for fastening said upper bolt to a mechanical test machine and constraining the movement of said upper bolt to the axial direction; a second ring for fastening said lower bolt to said mechanical test machine and constraining the movement of said lower bolt to the axial direction; a first collar with housings connected to said upper bolt; a second collar with housings connected to said lower bolt; a conductive target plate mounted in a said housing of said first collar in proximity to said test specimen such that the direction of the applied test load is perpendicular to the target surface of said conductive target plate; and a capacitive gauge sensor mounted in a said housing of said second collar in proximity to said test specimen such that the surface of said capacitive gauge sensor is vertically aligned with, and parallel to, said target surface of said conductive target plate forming a conductive target plate-capacitive gauge sensor pair, said conductive target plate-capacitive gauge sensor pair is positioned such that the distance between said target surface of said conductive target plate and said surface of said capacitive gauge sensor produces a signal that is within the measurement range of said capacitive gauge sensor, and upon commencement of a test, the amplitude of the voltage at said capacitive gauge sensor is proportional to the distance between said target surface of said conductive target plate and said surface of said capacitive gauge sensor and represents the dimensional change induced in said test specimen.