Method and apparatus for measuring relative hydration of a substrate

• US 6,370,426 B1
• Filed: 04/20/2000
• Issued: 04/09/2002
• Est. Priority Date: 04/20/1999
• Status: Expired due to Term

• Current Assignee: Nova Technology Corporation (Baker Hughes Company)
• Original Assignee: Nova Technology Corporation (Baker Hughes Company)
• Inventors: Nickson, Steven W., Campbell, Michael J. E., Sheppe, Richard W. Jr., Giguere, Dennis D., Gallant, Michael L., Horgan, Thomas B.
• Primary Examiner(s): Shaver, Kevin
• Assistant Examiner(s): MARMOR II, CHARLES ALAN
• Application Number:
  US09/552,972
• Time in Patent Office: 719 Days
• Field of Search: 600/306, 600/307, 600/547, 600/554, 600/557, 324/664, 324/688, 324/689, 324/692, 324/694, 324/696
• US Class Current: 600/547
• CPC Class Codes: A61B 5/0531 Measuring skin impedance
• CPC Class Codes: A61B 5/442 Evaluating skin mechanical properties, e.g. elasticity, hardness, texture, wrinkle assessment

Abstract

A method and apparatus for measuring relative hydration of a substrate. Measurements of the electrical characteristics of the substrate and the force applied to and the temperature of the substrate during the measurement provide inputs for determining such relative hydration of the substrate.

Claims

1. A system for measuring the relative hydration of a substrate comprising:

A) a probe having first and second electrodes for contacting the substrate at a site for which a measurement is desired,

B) an electrical impedance measurement circuit for periodically generating a value representing substrate impedance between the first and second electrodes,

C) an environmental factor measurement circuit for periodically generating a value representing a substrate environmental factor associated with the impedance measurement, and

D) a substrate hydration calculator for combining the impedance and environmental factor signals to generate an output representing the relative hydration of the substrate.

2. A system as recited in claim 1 wherein the environmental factor is substrate temperature and said environmental factor measuring circuit includes a temperature sensor in said probe for generating a signal representing substrate temperature at the site.

3. A system as recited in claim 1 wherein the environmental factor is a force with which said probe is applied to the substrate and said environmental factor measuring circuit includes a force sensor for measuring force applied to one of said electrodes.

4. A system as recited in claim 3 additionally comprising a temperature sensor in said probe for generating a signal representing substrate temperature at the site.

18. A method as recited in claim 1 wherein said environmental factor is substrate temperature and said environmental factor measuring includes measuring the temperature of the substrate at the site of said electrical characteristic measurement.

19. A method as recited in claim 1 wherein said substrate electrical characteristics measurement includes applying an electrical impedance sensor to a site of the substrate and said environmental factor is the force with which the impedance sensor is applied to the substrate, said environmental factor measuring including measuring the force on the impedance sensor at the site of the electrical impedance sensor measurement.

20. A method as recited in claim 1 wherein said environmental factor measuring includes measuring the temperature of the substrate at the site of the electrical impedance characteristics measurement.

21. A method as recited in claim 1 wherein said electrical characteristic measuring step includes:

i) applying a probe with first and second electrodes to a site of the substrate, and

ii) iteratively measuring the impedance of the substrate between the electrodes at the site.

22. A method as recited in claim 21 wherein said environmental factor is the substrate temperature and said environmental factor measuring includes iteratively measuring the temperature of the substrate at the site of said electrical impedance measurement concurrently with said iterative impedance measurement.

23. A method as recited in claim 21 wherein said environmental factor is a force with which the probe is applied to the site and said environmental factor measuring includes iteratively measuring the force of the probe at the site of the electrical impedance measurement.

24. A method as recited in claim 23 additionally comprising the step of iteratively measuring substrate temperature at the site of the electrical impedance measurement.

5. A system for measuring the relative hydration of a substrate including a measurement probe and a data processing system wherein said measurement probe comprises:

A) an elongated probe housing,

B) a sensor body mounted at one end of said probe housing with first and second concentric electrodes for contacting the substrate at a site for which a measurement is desired,

C) an electrical impedance measurement circuit in said probe housing for generating an impedance signal representing substrate impedance between the first and second electrodes,

D) a force sensor in said probe housing for generating a signal representing a force exerted by one of said electrodes on the substrate,

E) a signal processor in said probe housing for polling said electrical impedance measurement circuit and said force sensor thereby to generate processed impedance and force measurement signals, and

F) a connector at the other end of said probe housing for enabling communications of the processed impedance and force measurement signals to said data processing system from said signal processor whereby the data processing system combines the processed impedance and force measurement signals to produce a measurement of relative hydration.

6. A system as recited in claim 5 wherein said probe housing lies along an axis, said first electrode comprises a central conductor lying on the axis and said second electrode comprises a conductor coaxial with and spaced from said central conductor, said probe additionally including an insulatory between said central and coaxial conductors.

7. A system as recited in claim 6 wherein said sensor body extends between a first end that contacts the substrate and a second end proximate said probe housing, said force sensor comprising:

i) a support attached at the second end of said sensor body transverse to the axis, and

ii) a displacement force transducer on said support and contacting said sensor body whereby any force applied to the first end of said sensor body is transmitted through said coaxial conductor to said force transducer.

8. A system as recited in claim 7 wherein said probe is adapted to undergo a specified range of forces having first and second ends and wherein said signal processor includes first and second storage registers for the signal values from said force transducer when the force applied to said coaxial conductor is at the first and second ends of the force range, respectively.

9. A system as recited in claim 7 additionally comprising a temperature sensor in said sensor body to sense substrate temperature proximate the site at which said electrodes contact the substrate, said signal processor additionally including a circuit for generating a processed temperature signal for transfer to the data processing system.

10. A system as recited in claim 9 wherein said probe is adapted to operate under a specified range of substrate temperatures having first and second ends and wherein said signal processor includes third and fourth storage registers for the signal values from said temperature sensor when the temperature applied to said temperature sensor is at the first and second ends of the substrate temperature range, respectively.

11. A system as recited in claim 9 wherein said signal processor provides outputs for each of the impedance, force and temperature readings and wherein said data processing system includes means for requesting the transfer of each of the readings.

12. A system as recited in claim 9 wherein said signal processor provides outputs for each of the impedance, force and temperature readings and wherein said data processing system includes means for requesting the transfer of each of the readings on an iterative basis.

13. A system for measuring relative hydration of a substrate including a measurement probe and a data processing system wherein said measurement probe comprises:

A) an elongated probe housing extending between first and second ends,

B) a sensor body mounted at the first end of said probe housing with first and second concentric electrodes for contacting the substrate at a site for which a moisture measurement is desired,

C) an electrical impedance measurement circuit in said probe housing for generating an impedance signal representing substrate impedance between the first and second electrodes,

D) a temperature sensor in said probe housing for generating a signal representing substrate temperature contacting said electrodes,

E) a signal processor in said probe housing for polling said electrical impedance measurement circuit and said temperature sensor thereby to generate processed impedance and temperature measurement signals, and

F) a connector at the second end of said probe housing for enabling communications between said data processing system and said signal processor whereby the data processing system combines the processed impedance and temperature signals to produce a measurement of relative hydration.

14. A system as recited in claim 13 wherein probe housing lies along an axis, said first electrode comprises a central conductor lying on the axis and said second electrode comprises a conductor coaxial with and spaced from said central conductor, said probe additionally including an insulator between said central and coaxial conductors.

15. A system as recited in claim 14 wherein said probe is adapted to operate under a specified range of substrate temperatures having first and second ends and wherein said signal processor includes first and second storage registers for the signal values from said temperature sensor when the temperature applied to said temperature sensor is at the first and second ends of the temperature range, respectively.

16. A system as recited in claim 15 wherein said signal processor provides outputs for each of the impedance and temperature readings and wherein said data processing system includes means for requesting the transfer of each of the readings.

17. A method for measuring relative hydration of a substrate comprising the steps of:

A) measuring electrical characteristics of the substrate between electrodes contacting the substrate,

B) measuring an environmental factor of the substrate concurrently with said measurement of electrical characteristics, and

C) utilizing the measurements for said electrical characteristics and environmental factor measurements for obtaining a substrate impedance value that represents relative hydration of the substrate.