Methods and apparatus for determining properties of a fluid

• US 20060277979A1
• Filed: 06/08/2005
• Published: 12/14/2006
• Est. Priority Date: 06/08/2005
• Status: Active Grant

• Current Assignee: ProterixBio, Inc.
• Original Assignee: BioScale, Inc.
• Inventors: Wenzel, Stuart, Fitch, Eric
• Granted Patent: US 7,263,874 B2
• Time in Patent Office: Days
• US Class Current: 73/54.410
• CPC Class Codes: G01N 11/16 by measuring damping effect upon oscillatory body
• 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 method and system for determining properties of a fluid involves interacting the fluid with a standing wave in a first state to establish the standing wave in a second state, analyzing an electric signal associated with the standing wave to determine a characteristic associated with the second state, and determining the property of the fluid by comparing the characteristic with a function that associates a plurality of properties with a corresponding plurality of characteristics. The characteristic can include a maximum phase slope, a phase slope associated with a resonant frequency, a maximum magnitude associated with the resonant frequency, the value of the resonant frequency, or any combination thereof.

Claims

1. A method for determining viscosity of a fluid comprising:

interacting the fluid with a standing wave in a first state to establish the standing wave in a second state;

analyzing an electric signal associated with the standing wave to determine a characteristic associated with the second state, wherein the characteristic comprises at least one of a maximum phase slope of at least a part of the electric signal, a phase slope associated with a resonant frequency, or both; and

determining the viscosity of the fluid by comparing the characteristic associated with the second state with a function that associates a plurality of viscosities with a corresponding plurality of characteristics.

2. The method of claim 1, wherein a wave speed associated with the standing wave is less than the speed of sound in the fluid.

3. The method of claim 1, wherein the function is a calibration function that associates a plurality of known viscosities with a corresponding plurality of known characteristics.

4. The method of claim 1, further comprising:

determining density of the fluid by comparing the resonant frequency with a second function that associates a plurality of densities with a corresponding plurality of resonant frequencies.

5. The method of claim 4, wherein the second function is a calibration function that associates a plurality of known densities with a corresponding plurality of known resonant frequencies.

6. The method of claim 4, wherein the viscosity is the dynamic viscosity of the fluid, and further comprising:

determining the kinematic viscosity of the fluid by relating the density of the fluid and the dynamic viscosity of the fluid.

7. The method of claim 4, wherein the viscosity is the kinematic viscosity of the fluid, and further comprising:

determining the dynamic viscosity of the fluid by relating the density of the fluid and the kinematic viscosity of the fluid.

8. The method of claim 1, wherein the function comprises a lookup table or a mathematical formula.

9. The method of claim 1, wherein analyzing further comprises:

conducting at least a first sweep through a bandwidth of frequencies of the standing wave to determine at least two phase values associated with at least two corresponding frequency values of the second state; and

providing a phase function for relating each of the phase values to the at least two frequency values, wherein the maximum of the phase slope is defined as a phase value at which a derivative of the phase function is a relative extreme.

10. The method of claim 1, wherein analyzing further comprises:

conducting at least a first sweep through a bandwidth of frequencies of the standing wave to locate the resonant frequency;

determining a phase value associated with the resonant frequency; and

defining the maximum of the phase slope as the phase value associated with the resonant frequency.

11. The method of claim 1, wherein the electric signal is produced by an acoustic wave device.

12. The method of claim 11, wherein the acoustic wave device is a flexural plate wave device.

13. The method of claim 1, wherein interacting further comprises providing one or more tone bursts to an acoustic wave device to generate the standing wave.

14. The method of claim 1, wherein determining viscosity of the fluid comprises comparing the temperature of the fluid with a second function that associates a plurality of temperatures with a second corresponding plurality of viscosities.

15. A method for determining viscosity of a fluid comprising:

interacting the fluid with a standing wave in a first state to establish the standing wave in a second state, wherein a wave speed associated with the standing wave is less than the speed of sound in the fluid;

analyzing an electric signal associated with the standing wave to determine a characteristic associated with the second state, wherein the characteristic comprises a maximum magnitude of at least a part of the electric signal associated with a resonant frequency of the electric signal; and

determining viscosity of the fluid by comparing the characteristic associated with the second state with a function that associates a plurality of viscosities with a corresponding plurality of characteristics.

16. The method of claim 15, wherein analyzing further comprises:

conducting at least a first sweep through a bandwidth of frequencies of the standing wave to determine at least two magnitude values associated with at least two corresponding frequency values of the second state; and

providing a magnitude function for relating each of the at least two corresponding frequency values to the at least two magnitude values, wherein the resonant frequency is defined as a frequency value at which a derivative with respect to frequency of the magnitude function is approximately zero.

17. The method of claim 15, wherein determining the viscosity of the fluid comprises comparing the temperature of the fluid with a second function that associates a plurality of temperatures with a second corresponding plurality of viscosities.

18. A method for determining density of a fluid comprising:

interacting the fluid with a standing wave in a first state to establish the standing wave in a second state;

analyzing an electric signal associated with the standing wave to determine a resonant frequency associated with the second state; and

determining density of the fluid by comparing the resonant frequency with a function that associates a plurality of densities with a corresponding plurality of resonant frequencies.

19. The method of claim 18, wherein analyzing further comprises:

conducting at least a first sweep through a bandwidth of frequencies of the standing wave to determine at least two magnitude values associated with at least two corresponding frequency values of the second state; and

providing a magnitude function for relating each of the at least two frequency values to the at least two magnitude values, wherein the resonant frequency is defined as a frequency value at which a derivative of the magnitude function is approximately zero.

20. The method of claim 18, wherein analyzing further comprises:

conducting at least a first sweep through a bandwidth of frequencies of the standing wave to determine at least two phase values associated with at least two corresponding frequency values of the second state; and

providing a phase function for relating each of the at least two corresponding frequency values to the at least two phase values, wherein the resonant frequency is defined as a frequency value at which a derivative of the phase function is a relative extreme.

21. The method of claim 18, wherein determining the density of the fluid comprises comparing the temperature of the fluid with a second function that associates a plurality of temperatures with a second corresponding plurality of densities.

22. An apparatus for determining viscosity of a fluid, the device comprising:

a means for interacting a fluid with a standing wave in a first state to establish the standing wave in a second state;

a means for analyzing an electric signal associated with the standing wave to determine a characteristic associated with the second state, wherein the characteristic comprises at least one of a maximum phase slope, a phase slope associated with a resonant frequency, or both;

a means for determining viscosity of the fluid by comparing the characteristic associated with the second state with a function that associates a plurality of viscosities with a corresponding plurality of characteristics.