Viscosity measurements of viscous liquids using magnetoelastic thick-film sensors

A ribbon-like magnetoelastic thick-film sensor can be considered the magnetic analog of an acoustic bell. In response to an externally applied magnetic field impulse the magnetoelastic sensor magnetically rings, in a bell-like fashion, emitting magnetic flux with a characteristic resonant frequency that is determined from a fast Fourier transform of the transient response captured using a pickup coil. The resonant frequency of the sensor changes in response to mass loading and, when immersed in liquid, interfacial shear forces associated with viscosity. We report on the use of magnetoelastic sensors to measure the viscosity and density of highly viscous liquids. When characterizing highly viscous liquids, to avoid over damping of the sensor due to the liquid mass load the sensor is suspended from a boat-like structure with one end of the sensor immersed a fixed distance into the liquid. Using this method liquid viscosities ranging from 1.3 to 12 P are measured. (C) 2000 American Institute of Physics. [S0034-6748(00)01603-8].