Method of sensing strain in a material by driving an embedded magnetoelastic film-coated wire to saturation

A method of sensing strain in a material, said method comprising the steps of:

• (a) embedding in a material at least one wire formed of a conductive core and a magnetoelastic film coated around the conductive core and having a known level of saturation;
• (b) interconnecting an input lead to one end portion of the wire and an output lead to another end portion of the wire;
• (c) inputting an electrical current in the wire through the input lead so as to drive the magnetoelastic film of the wire to saturation such that the electrical impedance is sensitive to changes in strain in the material, thereby causing a highly non-linear increase in impedance of the wire;
• and
• (d) outputting an electrical voltage signal from the output lead, said output voltage signal having a spike which changes in amplitude to a strain imposed on the material surrounding the wire.