Rheological testing apparatus and method

• US 4,691,714 A
• Filed: 04/08/1986
• Issued: 09/08/1987
• Est. Priority Date: 10/15/1984
• Status: Expired due to Fees

• Current Assignee: Adamtek Corporation, Hibshman Corporation (Dynasil Corp. of America)
• Original Assignee: Adamtek Corporation, Hibshman Corporation (Dynasil Corp. of America)
• Inventors: Wong, Marcus Y., Motamedi, M. Ed, Wong, Jacob Y., Khuri-Yakub, Pierre
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): Jaworski, Francis J.
• Application Number:
  US06/850,077
• Time in Patent Office: 518 Days
• Field of Search: 128/632, 128/637, 128/660, 128/736, 128/738, 73/1 R, 73/1 G, 73/29, 73/32 R, 73/32 A, 73/54, 73/61.2, 73/64.1, 73/73, 73/570, 73/590, 73/335, 73/336.5, 374/117, 310/313 R, 310/313 B
• US Class Current: 600/551
• CPC Class Codes: A61B 10/0012 Ovulation-period determination for animals A61D17/002
• CPC Class Codes: A61B 2010/0019 based on measurement of temperature
• CPC Class Codes: A61B 2010/0022 based on measurement of viscosity or visco-elasticity
• CPC Class Codes: A61B 2562/0204 Acoustic sensors
• CPC Class Codes: A61B 2562/0271 Thermal or temperature sensors
• CPC Class Codes: A61B 5/103 Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes A61B5/08 takes precedence; measuring aids for tailors A41H1/00; measuring instruments specially adapted for dentistry A61C19/04
• CPC Class Codes: A61B 5/6847 mounted on an invasive device
• CPC Class Codes: A61B 8/12 in body cavities or body tracts, e.g. by using catheters catheters per se A61M25/00

Abstract

The device electronically measures fluid viscosity and temperature simultaneously principally for determining the changes in the properties of cervical mucus at the onset of ovulation. Interdigital transducers are used to generate and detect surface and bulk acoustic waves on one side of a slab of fused quartz. The change of phase of surface acoustic waves and the change in amplitude of doubly-reflected bulk acoustic waves are used to detect respectively the temperature and viscosity of fluid sample deposited on the opposite face of the slab.

Claims

1. A device for measuring fluid viscosity comprising:

(a) an inert slab having a first face exposable to the fluid;

(b) acoustic wave generating means on a second face of the slab for generating a bulk wave toward the first face;

(c) receiving means on the slab in the path of the bulk wave after it reflects from the first face for receiving the reflected bulk wave from the first face and generating a first output;

(d) first circuit means attached to the receiving means for measuring the amplitude of the first output and comparing the first output to a first reference output whereby the difference between the first output and the first reference output is a function of the viscosity of the fluid in contact with the first face.

2. The device of claim 1 further comprising the generating means generating a surface acoustic wave along the surface of the slab, the receiving means being positioned for receiving the surface acoustic wave and generating a second output;

and second circuit means attached to the receiving means for measuring the phase of the second output and comparing the second output to a second reference output whereby the difference between the second output and the second reference output is a function of the temperature of the slab.

3. The device of claim 1 wherein the acoustic wave generating means comprises an interdigital transducer on the second face of the slab opposite the first face.

4. The device of claim 3 wherein the receiving means comprises an interdigital transducer on the second face of the slab.

5. The device of claim 1, wherein the slab is formed of a non-piezoelectric material and the acoustic wave generating means and the receiving means each comprises a pair of electrodes adjacent each other on the second face to which high frequency alternating potential is respectively applied.

6. The device of claim 5 further comprising a layer of piezoelectric material over the electrodes and at least a portion of the slab contacting the electrodes for allowing the excitation of acoustic waves in the slab.

7. The device of claim 6 wherein the piezoelectric material is zinc oxide.

8. The device of claim 6 further comprising a metal plate over the piezoelectric material and the electrodes for enhancing the coupling of the acoustic energy into the slab.

9. The device of claim 8 wherein a portion of the metal plate is connected to the slab.

10. The device of claim 5 wherein each electrode has a base portion and a plurality of arms, each arm extending toward the opposite base and being spaced from the arms of the opposing electrode.

11. The device of claim 10 wherein the width of the arms and the spacing between arms of the opposing electrodes are such that the acoustic wave generating means generates bulk acoustic waves in the slab that reflect first off of the first face, then off of the second face, again off of the first face and then to the receiving means.

12. The device of claim 10 wherein the substrate is about 0.635 mm thick and 6.20 mm long, the distance between adjacent arms on the same electrode is about 0.025 mm, and wherein the device generates waves at about 39.3°

to the plane of the first face.

13. The device of claim 1 wherein the slab is formed of non-piezoelectric material, the acoustic wave generating means comprising a first electrode pair on the second face and piezoelectric material on the first electrode pair, and high frequency driving means connected to the first electrode pair for generating acoustic waves in the slab.

14. The device of claim 13 further comprising a metal plate over the piezoelectric material and the first electrode pair for enhancing the coupling of the acoustic energy into the slab.

15. The device of claim 13 wherein the receiving means comprises a second electrode pair of the second face, the device further comprising detecting means connected to the second electrode pair for measuring the amplitude and phase of the acoustic waves propagating through the slab.

16. The device of claim 1 wherein the acoustic wave generating means comprises a first electrode pair of the inert slab and a first oscillator for generating a first signal at a first frequency, first pulse means connected to the first oscillator for converting the first signal into a series of tone bursts, and means connecting the pulse means to the first electrode pair for generating the bulk wave in the inert slab.

17. The device of claim 16 further comprising a second oscillator for generating a second signal at a second frequency, second pulse means connected to the second oscillator for converting the second signal into a second series of tone bursts, and delay means between the first and second pulse means for delaying the tone bursts of the second pulse means to the inert slab.

18. The device of claim 17 further comprising detector means receiving signals from the first oscillator through the inert slab for detecting changes in amplitude of the first signal, the change in amplitude indicating the viscosity of fluid in contact with the device.

19. The device of claim 18 further comprising a phase detector for receiving a signal from the second oscillator through the inert slab for detecting changes in phase of the second series of tone bursts the changes in phase indicating the temperature of the device.

20. The device of claim 1 wherein the acoustic wave generating means comprises resonator means acoustically coupled to the slab for generating waves at a reference freuquency in the slab, the first circuit means receiving output signals from the resonator means and the slab, whereby changes in the amplitude of the first output is a function of the viscosity of the fluid in contact with the first face.

21. The device of claim 20 further comprising frequency detection means associated with the first circuit means for detecting the resonant frequency from the slab, the resonant frequency being a function of the of the temperature of fluid in contact with the slab.

22. A method of measuring the viscosity of a fluid comprising:

(a) placing the fluid on a slab of material;

(b) generating acoustic waves in the slab of material directed at the interface between the slab and the fluid thereby modulating the waves to form reflected waves;

(c) receiving the reflected waves to form a received signal;

(d) comparing the received signal with a known signal received for a viscosity of a given liquid for determining the viscosity of the tested liquid.

23. An instrument for rheological testing of cervical liquid comprising:

(a) a sensing transducer comprising an inert slab having a first face exposable to the liquid, wave generating means on a second face of the slab for generating a bulk wave toward the first face, receiving means on the slab in the path of the bulk wave after it reflects from the first face for receiving the reflected bulk wave from the first wave and generating a first output, first circuit means attached to the receiving means for measuring the amplitude of the first output and comparing the first output to a reference output whereby the difference between the first output and the reference output is a function of the viscosity of the liquid in contact with the first face; and

(b) support means for supporting the sensing transducer with the first face exposable to the cervical liquid, the support means being of a shape for insertion into a vagina for positioning the sensing transducer in contact with the cervical liquid.

24. The instrument of claim 23 wherein the support means includes means adjacent the sensing transducer for expanding the support means for moving the sensing transducer into contact with said cervical liquid.