Method and apparatus for characterizing materials by using a mechanical resonator

• US 6,494,079 B1
• Filed: 03/07/2001
• Issued: 12/17/2002
• Est. Priority Date: 03/07/2001
• Status: Expired due to Term

• Current Assignee: Meas France
• Original Assignee: Symyx Technologies Incorporated (Dassault Systemes SA)
• Inventors: Bennett, James, Matsiev, Leonid, McFarland, Eric
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): MILLER, ROSE MARY
• Application Number:
  US09/800,819
• Time in Patent Office: 650 Days
• Field of Search: 73/240.1, 73/240.3, 73/240.4, 73/240.5, 73/240.6, 73/300.1, 73/300.4, 73/310.1, 73/310.2, 73/310.3, 73/310.5, 73/310.6, 73/32.R, 73/32.A, 73/530.1, 73/540.1, 73/540.2, 73/542.3, 73/542.4, 73/542.5, 73/542.6, 73/543.8, 73/544.1, 73/614.5, 73/614.9, 73/617.5, 73/617.9, 735/79, 310/360, 310/316, 310/320, 422/68.1, 422/75, 422/98
• US Class Current: 73/24.05
• CPC Class Codes: B01J 2219/00704 integrated with the reactor apparatus
• CPC Class Codes: G01H 13/00 Measuring resonant frequency
• CPC Class Codes: G01N 11/16 by measuring damping effect upon oscillatory body
• CPC Class Codes: G01N 2009/006 vibrating tube, tuning fork
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/0224 Mixtures of three or more liquids
• CPC Class Codes: G01N 2291/0255 (Bio)chemical reactions, e.g. on biosensors
• CPC Class Codes: G01N 2291/0256 Adsorption, desorption, surface mass change, e.g. on biosensors
• CPC Class Codes: G01N 2291/02818 Density, viscosity
• CPC Class Codes: G01N 2291/0422 Shear waves, transverse waves, horizontally polarised waves
• CPC Class Codes: G01N 2291/0423 Surface waves, e.g. Rayleigh waves, Love waves
• CPC Class Codes: G01N 2291/0427 Flexural waves, plate waves, e.g. Lamb waves, tuning fork, cantilever
• CPC Class Codes: G01N 29/022 Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices microdevices per se B81B
• CPC Class Codes: G01N 29/036 by measuring frequency or resonance of acoustic waves
• CPC Class Codes: G01N 29/30 Arrangements for calibrating or comparing, e.g. with standard objects
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00
• CPC Class Codes: G01N 29/42 by frequency filtering or by tuning to resonant frequency
• CPC Class Codes: G01N 29/4418 with a model, e.g. best-fit, regression analysis
• CPC Class Codes: G01N 29/4427 with stored values, e.g. threshold values
• CPC Class Codes: G01N 29/4436 with a reference signal amplitude comparison G01N29/48
• 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
• CPC Class Codes: G01N 9/34 : by using elements moving through the fluid, e.g. vane
• CPC Class Codes: G10K 11/02 : Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators

Abstract

A method and apparatus for measuring properties of a fluid composition in a conduit includes a mechanical resonator connected to a measurement circuit. The measurement circuit provides a variable frequency input signal to the mechanical resonator, causing the mechanical resonator to oscillate. The input signal is then sent to the mechanical resonator and swept over a selected frequency range. The mechanical resonator'"'"'s response over the frequency range depends on various characteristics of the fluid being tested, such as the temperature, viscosity, and other physical properties.

Claims

1. A method for measuring a property of a fluid composition in a conduit, the method comprising:

placing a mechanical resonator, selected from the group consisting of tridents, cantilevers, torsion bars, length extension resonators, bimorphs, unimorphs, membrane resonators, surface acoustic wave devices, and tuning fork resonators, in the conduit such that at least a portion of the mechanical resonator is surrounded by the fluid composition in the conduit;

applying a variable frequency input signal to a measurement circuit coupled with the mechanical resonator to oscillate the mechanical resonator;

varying the frequency of the variable frequency input signal over a predetermined frequency range to obtain a frequency-dependent resonator response of the mechanical resonator; and

determining the property of the fluid compostion based in the mechanical resonator'"'"'s response.

2. The method of claim 1, further comprising the steps of:

calibrating the mechanical resonator against a standard fluid having known properties to obtain calibration data; and

determining the property of the fluid composition based on the calibration data.

3. The method of claim 1, further comprising placing a plurality of mechanical resonators in the placing step.

4. The method of claim 1, wherein said method measures a physical property of the fluid composition in the conduit.

5. The method of claim 4, wherein the physical property measured by said method is selected from the group consisting of specific weight, temperature and viscosity.

6. The method of claim 1, wherein the fluid is flowing through the conduit during the applying and varying steps.

7. A method for measuring a property of a fluid composition in a conduit, the method comprising:

placing a plurality of mechanical resonators, each being different from the other and being selected from the group consisting of tridents, cantilevers, torsion bars, length extension resonators, bimorphs, unimorphs, membrane resonators, surface acoustic wave devices, and tuning fork resonators, in the conduit such that at least a portion of each of the mechanical resonators is surrounded by the fluid composition in the conduit;

applying a variable frequency input signal to a measurement circuit coupled with the mechanical resonators to oscillate the mechanical resonators;

varying the frequency of the variable frequency input signal over a predetermined frequency range to obtain a frequency-dependent resonator response of the mechanical resonators; and

determining the property of the fluid composition based on the mechanical resonators'"'"' response.

8. A method for measuring a property of a fluid composition in a conduit, the method comprising:

placing a mechanical resonator in the conduit such that at least a portion of the mechanical resonator is surrounded by the fluid composition in the conduit;

applying a variable frequency input signal to a measurement circuit coupled with the mechanical resonator to oscillate the mechanical resonator;

varying the frequency of the variable frequency input signal over a predetermined frequency range to obtain a frequency-dependent resonator response of the mechanical resonator; and

determining the property of the fluid composition based on the mechanical resonator'"'"'s response;

wherein said resonator is a multiple-mode resonator that can be operated in more than one mechanical mode, and wherein the varying step comprises varying the frequency of the variable frequency input signal to obtain a plurality of frequency-dependent resonator responses corresponding to said more than one mechanical mode.

9. A method for measuring a property of a fluid composition in a conduit, the method comprising:

placing a mechanical resonator in the conduit such that at least a portion of the mechanical resonator is surrounded by the fluid composition in the conduit;

applying a variable frequency input signal to a measurement circuit coupled with the mechanical resonator to oscillate the mechanical resonator;

varying the frequency of the variable frequency input signal over a predetermined frequency range to obtain a frequency-dependent resonator response of the mechanical resonator; and

simultaneously determining an electrical property and a physical property of the fluid composition based on the mechanical resonator'"'"'s response.

10. The method of claim 9, wherein the electrical properties and physical properties measured by said method are selected from the group consisting of specific weight, viscosity, temperature, dielectric constant and conductivity.

11. The method of claim 10, wherein said method simultaneously measures at least two properties selected from the group consisting of specific weight, viscosity, temperature, dielectric constant and conductivity of the fluid composition in the conduit.

12. A method for measuring a property of a fluid composition in a conduit, the method comprising:

placing a mechanical resonator in the conduit such that at least a portion of the mechanical resonator is surrounded by the fluid composition in the conduit;

applying a variable frequency input signal to a measurement circuit coupled with the mechanical resonator to oscillate the mechanical resonator;

varying the frequency of the variable frequency input signal over a predetermined frequency range to obtain a frequency-dependent resonator response of the mechanical resonator;

calibrating the mechanical resonator against a standard fluid having known properties to obtain calibration data; and

determining the property of the fluid composition based on the mechanical resonator'"'"'s response and based on the calibration data.

13. A method for measuring a property of a fluid composition in a conduit, the method comprising:

placing a tuning fork resonator in the conduit such that at least a portion of the tuning fork resonator is surrounded by the fluid composition in the conduit;

applying a variable frequency input signal to a measurement circuit coupled with the tuning fork resonator to oscillate the mechanical resonator;

varying the frequency of the variable frequency input signal over a frequency range of 25 to 30 kHz to obtain a frequency-dependent resonator response of the tuning fork resonator; and

determining the property of the fluid composition based on the tuning fork resonator'"'"'s response.

14. A method for measuring a property of a fluid composition in a conduit, the method comprising:

placing a mechanical resonator, adapted to suppress the generation of acoustic waves in the fluid composition, in the conduit such that at least a portion of the mechanical resonator is surrounded by the fluid composition in the conduit;

applying a variable frequency input signal to a measurement circuit coupled with the mechanical resonator to oscillate the mechanical resonator;

varying the frequency of the variable frequency input signal over a frequency range of less than 1 MHz to obtain a frequency-dependent resonator response of the mechanical resonator; and

determining the property of the fluid composition based on the mechanical resonator'"'"'s response while the fluid composition is flowing through the conduit.