Patent ID: 7493827

Claim:
A method of determining a strain on a link comprising: providing a sensor including: a link, said link constructed of a first material, said link having a link longitudinal axis, a tube having a tube-longitudinal axis and attached to a surface on the link such that said link longitudinal axis and said tube longitudinal axis are approximately parallel, first and second members, said first and second members extending transversely across an interior portion of the tube at different locations and forming a sensor cavity within the tube, a first magnetically permeable core attached to said first member and extending transversely to said tube longitudinal axis and providing a pair of first spaced pole ends, each first pole end having a first spaced face, a second magnetically permeable core attached to said second member and extending transversely to said tube-longitudinal axis and providing a pair of second spaced pole ends, each second pole end having a second spaced face, each said second spaced face opposing its corresponding each said first spaced face and separated by a magnetic gap width, a first excitation coil wound around one of the first pole ends and a second excitation coil wound around the other first pole end using conductive wire, one end of the wire from each of the first and second excitation coils being conductively connected and the other end forming an excitation coil pair, said excitation coil pair connected to a cable extending through the tube, connectable to a supply voltage and predetermined capacitance in a resonant inductance-capacitance circuit, providing connection to an inductance which is variable as a function of the magnetic gap width and also as a function of relative displacement of said first and second members resulting from strain on the link along the link longitudinal axis; and measuring the inductance to determine a strain on the link.