Magneto-acoustic sensors for measurement of liquid temperature, viscosity and density

We report on a novel acoustic method for measurement of liquid temperature, viscosity and density using magneto-acoustic sensors. The sensors are comp rised of free-standing magnetoelastic thick films that oscillate in respons e to an externally applied time-varying magnetic field; depending upon the physical geometry and surface roughness of the film these mechanical deform ations launch an acoustic wave that can be detected remotely from the test area. These oscillations are strongest at the characteristic resonant frequ ency of the sensor, which shifts linearly in response to temperature and, w hen immersed in a liquid, the damping forces associated with liquid viscosi ty and density. (C) 2001 Elsevier Science Ltd. All rights reserved.