A temperature sensing apparatus including a sensor element made of a magnetically soft material operatively arranged within a first and second time-varying interrogation magnetic field, the first time-varying magnetic field being generated at a frequency higher than that for the second magnetic field....http://www.google.de/patents/US6639402?utm_source=gb-gplus-sharePatent US6639402 - Temperature, stress, and corrosive sensing apparatus utilizing harmonic response of magnetically soft sensor element (s)
