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AssigneeThe Board of Regents of the University of Washington
InventorsHarold E. Hager, J. D. Sheldon Danielson
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The disclosed system includes a piezoelectric crystal exposed to an energy-absorptive medium of interest. A crystal oscillation circuit is included for sustaining oscillation of the crystal in contact with the fluid. To accomplish this, the circuit includes feedback elements for providing automatic gain control of the amplifier portion of the oscillator. In this manner, the conditions required for crystal oscillation are maintained independent of variations in the medium the crystal is exposed to. Information regarding the gain adjustment and oscillation frequency of the crystal are applied to a microprocessor-based system for determining fluid characteristics such as viscosity, density, and dielectric constant. Alternatively, this information is used to correct for the influence of such parameters on the resonant behavior of piezoelectric crystals undergoing mass change, in the analysis of, for example, corrosion, adsorption and electroplating. The relationship between the particular characteristics determined and the output information received from the oscillation circuit is dependent upon the hydrodynamic and electrokinetic coupling experienced between the medium and crystal.
A system for monitoring the interaction between a piezoelectric element and an energy-absorptive medium of interest that said piezoelectric element is exposed to, said system comprising:
The system of clai 1, wherein said gain of said amplifier is representable by a complex number and said feedback means is representable by a transfer function that is a complex number, the product of the magnitudes of said gain and said transfer function being maintained substantially equal to positive one and the sum of the phase components of said gain and said transfer function being maintained substantially equal to zero by said feedback means.
A method of analyzing an absorptive medium comprising the steps of:
Dependencies are inferred from the claim text.