Remote query fluid-flow velocity measurement using magnetoelastic thick-film sensors (invited)

Abstract

The characteristic resonant frequency of a thick-film ribbon-shaped magnetoelastic sensor is dependent upon its length, density, Poisson’s ratio, and modulus of elasticity [J. M. Barandiaran and J. Guitierrez, Sens. Actuators A 59, 38 (1997)]. In a manner analogous to surface acoustic wave (SAW) sensors, this characteristic resonant frequency also changes with effective mass load or with friction force applied to the surface of the magnetoelastic sensor [L. D. Landau and E. M. Lifshitz, Theory of Elasticity, 3rd ed. (Pergamon, New York, 1986), Chap. II]. The time varying magnetic flux emitted from magnetoelastic sensors can be monitored remotely using pickup coils. Hence, in contrast with SAW devices, no direct physical connections are required to obtain magnetoelastic sensor information, allowing them to be monitored from within sealed, opaque containers. Reported here is application of magnetoelastic sensors to the measurement of fluid flow from within sealed pipes. Within the laminar fluid flow regime greater fluid velocity results in increased frictional drag on the surface of the sensor, which in turn lowers the resonant frequency of the magnetoelastic sensor.