Patent ID: 6172511
Filing Date: 2001-01-09
Classification: G01L,G01M

Abstract:
A device for measuring a crack in one of a workpiece and a sample comprising:a resistive layer having an impedance, said resistive layer being arranged to be fixed to said one of said workpiece and sample whereby in use, said resistive layer is fractured by said propagation of a crack in said one of said workpiece and sample thereby to change said impedance of said resistive layer;two elongate electrodes provided on said resistive layer, said two elongate electrodes being arranged in electrical contact with said resistive layer to pass a current through said resistive layer; andmeasuring means for measuring said impedance of said resistive layer, and for thereby determining a size of said crack in said one of said workpiece and sample from said measured impedance,said electrodes being curved whereby changes in said impedance of said resistive layer result in an approximately linear change in potential difference between said electrodes for substantially all directions of crack propagation.