Remote query measurement of pressure, fluid-flow velocity, and humidity using magnetoelastic thick-film sensors

Free-standing magnetoelastic thick-film sensors have a characteristic reson ant frequency that can be determined by monitoring the magnetic flux emitte d from the sensor in response to a time varying magnetic field. This proper ty allows the sensors to be monitored remotely without the use of direct ph ysical connections, such as wires, enabling measurement of environmental pa rameters from within sealed, opaque containers. In this work, we report on application of magnetoelastic sensors to measurement of atmospheric pressur e, fluid-flow velocity, temperature, and mass load. Mass loading effects ar e demonstrated by fabrication of a remote query humidity sensor, made by co ating the magnetoelastic thick film with a thin layer of solgel deposited A l2O3 that reversibly changes mass in response to humidity. (C) 2000 Elsevie r Science S.A. All rights reserved.