Conversion of liquid volume, density, and viscosity to frequency signals

Abstract

Volume of a working liquid in a sensing chamber is measured via a first mechanical resonance frequency. A second resonance may be measured to discriminate interacting volume and density effects, yielding corrected volume, density, and liquid mass. A probability of bubbles present in the liquid is indicated by an abnormal combination of first and second resonances. Determination of a frequency and an associated phase angle near a resonance may be used to discriminate interacting volume and viscosity effects, yielding corrected volume and viscosity. One boundary of the sensing chamber is a deformable plate, which may be rippled to increase the range of linear volumetric compliance. A second boundary paralleling the plate captures a thin variable-thickness fluid layer. Vibrations in the plate cause amplified fluid vibrations parallel to the plate surface, causing a high, thickness-sensitive fluid inertia that lowers plate resonance frequencies in a volume-sensitive manner. A transducer coupled to the resonant plate transforms the mechanical resonances into electrical resonances, which are electronically transformed into frequency readings. A first elastic barrier may contain liquid in a separable disposable container and conform directly to the mated vibrating plate, or to a second elastic barrier, which may be used, first, to retain working liquid on the sensing chamber side, and second, to couple volume changes via the working liquid into the sensing chamber from a second, measured liquid on the disposable side.

Dependencies are inferred from the claim text.