Remotely interrogated temperature sensors based on magnetic materials

A family of remotely interrogated passive temperature sensors is presented. These sensors are comprised of several layers of magnetic materials having either a resonant frequency or harmonic spectrum which varies with temperature. By incorporating a magnetic bias layer and a magnetically permeable layer, it is possible to create sensors which respond to a temperature threshold (reversibly or nonreversibly) or produce a signal which continuously and monotonically varies with temperature. In this paper, a 30%/70% Ni-Fe layer was used in conjunction with amorphous alloy strips to produce three distinct types of wireless temperature sensors operating over the range 20/spl deg/-70/spl deg/C.