Sensor, system, and method, for measuring fluid properties using Multi-Mode Quasi-Shear-Horizontal Resonator

• US 20090216467A1
• Filed: 02/22/2008
• Published: 08/27/2009
• Est. Priority Date: 02/22/2008
• Status: Active Grant

• Current Assignee: Knowles Capital Formation, Inc. (Knowles Corporation)
• Original Assignee: Delaware Capital Formation Incorporated (Dover Corporation)
• Inventors: Andle, Jeffrey C.
• Granted Patent: US 7,878,044 B2
• Time in Patent Office: Days
• US Class Current: 702/54
• CPC Class Codes: G01N 2011/0066 electrical properties
• CPC Class Codes: G01N 2203/0051 Piezoelectric means
• CPC Class Codes: G01N 2203/0075 Strain-stress relations or elastic constants
• CPC Class Codes: G01N 2203/0092 Visco-elasticity, solidification, curing, cross-linking degree, vulcanisation or strength properties of semi-solid materials
• CPC Class Codes: G01N 2203/0094 Visco-elasticity
• CPC Class Codes: G01N 9/002 using variation of the resonant frequency of an element vibrating in contact with the material submitted to analysis G01N9/34 takes precedence

Abstract

A system and a method for providing information on two of the three variables, density (ρ), viscosity (η), and elastic modulus (c) of a fluid, such that independent knowledge of one variable allows the remaining two variables to be measured by a single sensor. The present invention relies on the interaction of a predominantly shear horizontal acoustic wave device (“quasi-shear-horizontal”) with the fluid, so as to measure subtle differences in the interaction of two or more acoustic resonance states or waveguide modes of a multi-mode resonator or waveguide, and to derive the desired fluid characteristics therefrom. The most preferred embodiment is a dual-mode coupled resonator filter geometry with one resonant mode having a high degree of symmetry and the other having a high degree of anti-symmetry. By combining the additional information of multi-moded operation with the inherent ability of a horizontally-polarized quasi-shear-horizontal acoustic wave device (AWD) to operate in fluid environments, one obtains a multi-mode quasi-shear-horizontal (MMQSH) resonator.

Claims

1. A method of measuring at least two fluid properties selected from density, viscosity, and elastic modulus, when the third of said fluid properties is known or assumed, the method comprising the steps of:

providing a Multi Mode Quasi Shear Horizontal Resonator (MMQSHR) having an energy input, and a measuring surface for contacting said fluid, said measuring surface having at least a first region and a second region, and a separation area defined therebetween;

feeding said MMQSHR with excitation energy via said input, at a first and a second frequencies selected to excite a first and a second acoustic modes respectively, each of said acoustic modes causing a component of horizontal shear wave motion in said surface,

wherein excitation in said first frequency further causing said regions to move in phase relative to each other;

and wherein excitation in said second frequency causes said two regions to move out-of-phase relative to each other, inducing a vertical displacement in said separation area;

measuring energy related parameters at said first mode and second mode;

calculating two of said fluid properties utilizing said energy related parameters and information relating to said third fluid property.

2. A method as claimed in claim 1 wherein said energy related parameters are selected from a list consisting of insertion loss, frequency shift, phase shift, amplitude, current change, equivalent series resistance, or a combination thereof.

3. A method as claimed in claim 1, wherein said MMQSHR comprises a piezoelectric crystal, and wherein said input comprises an input transducer.

4. A method as claimed in claim 1, wherein said step of calculating occurs separately for each of said calculated fluid properties.

5. A method as claimed in claim 3, further comprising an output transducer, wherein said input transducer and said output transducer are referenced to an opposing ground electrode.

6. A method as claimed in claim 3, wherein said MMQSHR sensor employs a structure selected from a group consisting of bulk acoustic wave resonator, planar resonator, and shear horizontal surface acoustic wave resonator.

7. A method according to claim 1, wherein said elastic modulus is calculated according to the formula

8. A method according to claim 1, wherein said viscosity is calculated according to the formula

9. A method according to claim 1, wherein said density is calculated according to one of the formulae

10. A method according to claim 1, wherein said surface is corrugated, and further comprising the step of calculating said fluid density responsive to changes in energy related parameters due to fluid trapped in said corrugations.

11. A method as claimed in claim 1, wherein said step of feeding comprises providing excitation energy in combination with additional frequencies, so as to cause said surface to resonate at more frequencies than said first and second frequencies.

12. A method as claimed in claim 3, wherein said piezoelectric material is cut from a crystal so as to allow a plurality of shear modes responsive to said excitation.

13. A method as claimed in claim 1, wherein said MMQSHR comprises an electrically conductive material, and wherein said excitation energy is electromagnetic.

20. A method as claimed in claim 1, wherein said step of feeding comprises providing excitation energy in combination of differing power levels at the at least two frequencies, so as to cause said surface to impart various shear rates to the fluid at each of said frequencies, allowing the measurements to be made at varying shear rate.

14. A system for measuring at least two fluid properties selected from density, viscosity, and elastic modulus, when the third of said fluid properties is known or assumed, the system comprising:

A Multi-Mode Quasi Shear Horizontal (MMQSHR) resonator having

a measuring surface for contacting said fluid;

an energy input port and an energy output port;

at least a first region and a second region, and a separation area defined therebetween;

excitation circuitry coupled at least to said energy input, and constructed to impart two acoustic modes of resonant motion to said surface;

wherein said two acoustic modes are selected to cause differing amplitudes of motion normal to said surface, when excited at the resonant frequency of said different acoustic modes;

measurement circuitry constructed to measure at least one parameter of the energy inputted into the MMQSHR resonator or outputted therefrom; and

,

parameter calculating processor coupled to said measurement circuitry, and constructed to calculate at least said two fluid properties when said third fluid property is known or assumed.

15. A system as claimed in claim 14, wherein said energy input is coupled to electrical energy source, and further comprising optical or mechanical monitor to monitor displacement of said separation area, said monitor being coupled to said measurement circuitry.

16. A system as claimed in claim 14, further comprising calculator or computer circuitry for calculating said fluid properties, utilizing information obtained from said measurement circuitry.

17. A system as claimed in claim 14, wherein said MMQSHR comprises a piezoelectric monolithic crystal filter.

18. A system as claimed in claim 14, wherein said MMQSH comprises a piezoelectric transverse coupled resonator filter.

19. A system as claimed in claim 14, wherein said MMQSH comprises and electromagnetic acoustic transducer.

21. A resonator comprising a region of added mass defining trapped energy region, said trapped energy region supporting a plurality of laterally confined modes, said modes interacting with at least one transducer, said transducer providing electrical impedance relating to energy loss in said trapped energy resonator.

22. A fluid parameter measurement system comprising:

a biasing magnetic field;

an oscillating magnetic field;

a resonator comprising;

at least a conducting surface region;

an energy trapping structure for placement within said biasing and oscillating magnetic fields, wherein said oscillating magnetic field causes eddy currents within said conducting surface region;

said eddy currents interacting with said biasing magnetic field, creating a time-harmonic force field within said resonator; and

wherein said force field imparts quasi shear horizontal acoustic waves at a surface of said resonator, said acoustic wave having at least a first and a second frequency respectively;

said first frequency selected to cause at least a first region of said surface, and a second region of said surface to move in phase relative to each other, said first and second regions having a first separation area interspersed therebetween;

said second frequency selected to cause a third region of said surface and a fourth region of said surface to move out of phase relative to each other, said first and second regions having a second separation area interspersed therebetween, wherein imparting energy to cause resonance at said second frequency induces a vertical displacement in said second separation area;

said system further comprises a tracker constructed to track the displacement of selected regions of said surface.

23. A system as claimed in claim 22, wherein said first separation area is in registration with said second registration area.