Sens Actuators A Phys
· 2002 Aug · PMID 12398065
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The resonant frequency and quality factor Q of a liquid immersed magnetoelastic sensor are shown to shift linearly with the liquid viscosity and density product. Measurements using different grade oils, organic chemicals...The resonant frequency and quality factor Q of a liquid immersed magnetoelastic sensor are shown to shift linearly with the liquid viscosity and density product. Measurements using different grade oils, organic chemicals, and glycerol-water mixtures show that the surface roughness of the sensor in combination with the molecular size of the liquid play important roles in determining measurement sensitivity, which can be controlled through adjusting the surface roughness of the sensor surface. A theoretical model describing the sensor resonant frequency and quality factor Q as a function of liquid properties is developed using a novel equivalent circuit approach. Experimental results are in agreement with theory when the liquid molecule size is larger than the average surface roughness. However, when the molecular size of the liquid is small relative to the surface roughness features molecules are trapped, and the trapped molecules act both as a mass load and viscous load; the result is higher viscous damping of the sensor than expected.
Sens Actuators A Phys
· 2000 Sep · PMID 12143886
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Free-standing magnetoelastic thick-film sensors have a characteristic resonant frequency that can be determined by monitoring the magnetic flux emitted from the sensor in response to a time varying magnetic field. This p...Free-standing magnetoelastic thick-film sensors have a characteristic resonant frequency that can be determined by monitoring the magnetic flux emitted from the sensor in response to a time varying magnetic field. This property allows the sensors to be monitored remotely without the use of direct physical connections, such as wires, enabling measurement of environmental parameters from within sealed, opaque containers. In this work, we report on application of magnetoelastic sensors to measurement of atmospheric pressure, fluid-flow velocity, temperature, and mass load. Mass loading effects are demonstrated by fabrication of a remote query humidity sensor, made by coating the magnetoelastic thick film with a thin layer of solgel deposited Al2O3 that reversibly changes mass in response to humidity.
Sens Actuators A Phys
· 2000 Mar · PMID 12143885
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Magnetically soft, magnetostrictive metallic glass ribbons are used as in-situ remote query viscosity sensors. When immersed in a liquid, changes in the resonant frequency of the ribbon-like sensors are shown to correlat...Magnetically soft, magnetostrictive metallic glass ribbons are used as in-situ remote query viscosity sensors. When immersed in a liquid, changes in the resonant frequency of the ribbon-like sensors are shown to correlate with the square root of the liquid viscosity and density product. An elastic wave model is presented that describes the sensor response as a function of the frictional forces acting upon the sensor surface.
Sens Actuators A Phys
· 2001 Nov · PMID 12143884
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Application of magnetoelastic thick-film sensors to the measurement of thin-film elastic moduli is described in this study. An analytical model is derived, that relates the resonant frequency of a magnetoelastic sensor t...Application of magnetoelastic thick-film sensors to the measurement of thin-film elastic moduli is described in this study. An analytical model is derived, that relates the resonant frequency of a magnetoelastic sensor to the elasticity and density of an applied thin-film. Limits of the model are analyzed, and related to experimental measurements using thin-films of silver and aluminum. For 500 nm thick-films, the measured Young's modulus of elasticity for Al and Ag is found to be within 1.6% of standard data. Using commercially available magnetoelastic sensors, the elasticity of coatings, approximately 30 nm thick, can readily be measured.