Temperature, stress, and corrosive sensing apparatus utilizing harmonic response of magnetically soft sensor element (s)

• US 6,639,402 B2
• Filed: 01/31/2002
• Issued: 10/28/2003
• Est. Priority Date: 01/31/2001
• Status: Expired due to Fees

• Current Assignee: University Of Kentucky Research Foundation (University of Kentucky)
• Original Assignee: University Of Kentucky Research Foundation (University of Kentucky)
• Inventors: Ong, Keat Ghee, Grimes, Craig A.
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US10/061,840
• Publication Number:
  US 20020153882A1
• Time in Patent Office: 635 Days
• Field of Search: 324/239, 324/209, 324/232, 324/262, 737/68, 737/79, 436/149, 374/117, 374/163
• US Class Current: 324/239
• CPC Class Codes: G01N 17/00 Investigating resistance of materials to the weather, to corrosion, or to light
• CPC Class Codes: G01N 27/72 by investigating magnetic variables

Abstract

A temperature sensing apparatus including a sensor element made of a magnetically soft material operatively arranged within a first and second time-varying interrogation magnetic field, the first time-varying magnetic field being generated at a frequency higher than that for the second magnetic field. A receiver, remote from the sensor element, is engaged to measure intensity of electromagnetic emissions from the sensor element to identify a relative maximum amplitude value for each of a plurality of higher-order harmonic frequency amplitudes so measured. A unit then determines a value for temperature (or other parameter of interst) using the relative maximum harmonic amplitude values identified. In other aspects of the invention, the focus is on an apparatus and technique for determining a value for of stress condition of a solid analyte and for determining a value for corrosion, using the relative maximum harmonic amplitude values identified. A magnetically hard element supporting a biasing field adjacent the magnetically soft sensor element can be included.

Claims

1. A temperature sensing apparatus, comprising:

a sensor element made of a magnetically soft material operatively arranged within a first and second time-varying interrogation magnetic field, said first time-varying magnetic field being generated at a frequency higher than that for said second magnetic field;

a receiver, remote from said sensor element, to measure intensity of electromagnetic emissions from said sensor element to identify a relative maximum amplitude value for each of a plurality of higher-order harmonic frequency amplitudes so measured; and

a unit to determine a value for temperature using said relative maximum harmonic amplitude values identified.

2. The apparatus of claim 1 wherein said higher frequency of said first field is at least ten times greater than said second magnetic field frequency;

said unit comprises a processor, and said temperature value, T, is determined according to the expression;

$T=\frac{1}{{\left(N-1\right)}^2-N}<br><br>\underset{i=2}{\overset{N}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\underset{j=2}{\overset{N}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{f_i<br><br>a_j-f_j<br><br>a_i}{f_j<br><br>s_i-f_i<br><br>s_j}<br><br>\text{\hspace{1em}<br><br>}<br><br>i\ne <br><br>j.$

3. The apparatus of claim 1 wherein said receiver comprises an electromagnetic pick-up coil and a spectrum analyzer, said sensor element is elongated in shape, and a pre-correlation made between a series of comparative relative maximum harmonic amplitude values and a corresponding series of temperature values is used to determine said temperature value.

4. The apparatus of claim 3 wherein a width, w, of said elongated sensor element is less than three times a length thereof, e;

said receiver further comprises a spectrum analyzer, and said pre-correlation was made for a calibration sensor element of like size and material characteristics of said sensor element.

5. The apparatus of claim 1 wherein said higher frequency of said first field is selected from a first range of frequencies from 50 Hz to 10 MHz and said frequency of said second field is selected from a second range of frequencies from 0.1 Hz to 10 Hz;

and further comprising a computerized device for instructing said receiver to take, over a time interval, a series of sensor element emission measurements, and communicate each of a series of corresponding temperature values for said series of emission measurements taken.

6. The apparatus of claim 1 wherein the sensor element is located within a solid analyte, said value for temperature represents a localized temperature of said solid analyte, and said solid analyte comprises a component of a material selected from the group consisting of concrete, mortar, tar, wood, fiberboard, particleboard, plasterboard, sheetrock, fiberglass, plexiglass, resins, and plastics.

7. The apparatus of claim 6 wherein:

the said sensor element is elongated, having a length, e, from 1 mm to 1000 mm, and is made of a ferromagnetic alloy;

said solid analyte comprises a laminate of at least two components from said group; and

said sensor element is at least partially encapsulated within a corrosion-resistant casing and is interposed between said two components.

8. The apparatus of claim 6 wherein the said sensor element is elongated, having a length, e, from 1 mm to 1000 mm, and is embedded within said solid analyte, and said temperature value, T, is determined according to the expression:

$T=\frac{1}{{\left(N-1\right)}^2-N}<br><br>\underset{i=2}{\overset{N}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\underset{j=2}{\overset{N}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{f_i<br><br>a_j-f_j<br><br>a_i}{f_j<br><br>s_i-f_i<br><br>s_j}<br><br>\text{\hspace{1em}<br><br>}<br><br>i\ne <br><br>j.$

9. The apparatus of claim 1 wherein the sensor element is located on a surface of a solid analyte, said value for temperature represents a localized surface temperature of said solid analyte, and said solid analyte comprises a component of a material selected from the group consisting of concrete, mortar, tar, wood, fiberboard, particleboard, plasterboard, sheetrock, fiberglass, plexiglass, resins, and plastics.

10. The apparatus of claim 1 further comprising a magnetically hard element supporting a biasing field adjacent said magnetically soft sensor element, said magnetically hard element comprised of a material chemically responsive to a fluid analyte such that exposure thereto causes a change in said biasing field.

11. The apparatus of claim 1 wherein said first time-varying interrogation magnetic field comprises a signal-burst generated at said higher frequency, said measure of emissions is performed while sweeping said second time-varying field and while said signal-burst is transmitted by an interrogation field generating coil, said interrogation field generating coil is adapted for generating said second field, and said plurality of higher-order harmonic amplitudes so measured are for harmonics selected from a range of 2 to 100 times a fundamental resonant frequency for said sensor element.

12. An apparatus for sensing stress conditions of a solid analyte, comprising:

a sensor element made of a magnetically soft material operatively arranged within a first and second time-varying interrogation magnetic field, said first time-varying magnetic field being generated at a frequency higher than that for said second magnetic field;

a receiver, remote from said sensor element, to measure intensity of electromagnetic emissions from said sensor element to identify a relative maximum amplitude value for each of a plurality of higher-order harmonic frequency amplitudes so measured; and

a unit to determine a value for stress conditions of the analyte in proximity to said sensor element using said relative maximum harmonic amplitude values identified.

13. The apparatus of claim 12 wherein said higher frequency of said first field is at least ten times greater than said second magnetic field frequency;

said unit comprises a processor, said magnetically soft material comprises a ferromagnetic alloy, and a pre-correlation made for a calibration sensor element of like size and material characteristics of said sensor element is used to determine said stress conditions value.

14. The apparatus of claim 12 wherein said higher frequency of said first field is selected from a first range of frequencies from 50 Hz to 10 MHz and said frequency of said second field is selected from a second range of frequencies from 0.1 Hz to 10 Hz;

and further comprising a computerized device for instructing said receiver to take, over a time interval, a series of sensor element emission measurements, and communicate each of a series of corresponding stress condition values for said series of emission measurements taken.

15. The apparatus of claim 12 wherein the sensor element is made of a ferromagnetic alloy, is elongated, and is located within a solid analyte, and said value for stress conditions represents a localized stress within said solid analyte.

16. The apparatus of claim 15 wherein:

said sensor element is embedded within said solid analyte, said solid analyte comprises a component of a material selected from the group consisting of concrete, mortar, tar, wood, fiberboard, particleboard, plasterboard, sheetrock, fiberglass, plexiglass, resins, and plastics;

said plurality of higher-order harmonic amplitudes so measured are for harmonics selected from a range of 2 to 100 times a fundamental resonant frequency for said sensor element; and

said sensor element is at least partially encapsulated within a corrosion-resistant casing.

17. The apparatus of claim 12 wherein the sensor element is located on a surface of a solid analyte, said value for stress conditions represents a localized surface stress of said solid analyte, and said solid analyte comprises a component of a material selected from the group consisting of concrete, mortar, tar, wood, fiberboard, particleboard, plasterboard, sheetrock, fiberglass, plexiglass, resins, and plastics.

18. The apparatus of claim 12 further comprising a magnetically hard element supporting a biasing field adjacent said magnetically soft sensor element, said magnetically hard element comprised of a material chemically responsive to a fluid analyte such that exposure thereto causes a change in said biasing field.

19. The apparatus of claim 12 wherein said first time-varying interrogation magnetic field comprises a signal-burst generated at said higher frequency, said measure of emissions is performed while sweeping said second time-varying field and while said signal-burst is transmitted by an interrogation field generating coil, said interrogation field generating coil is adapted for generating said second field, and said plurality of higher-order harmonic amplitudes so measured are for harmonics selected from a range of 2 to 100 times a fundamental resonant frequency for said sensor element.

28. The apparatus of claim 19 wherein said first time-varying interrogation magnetic field comprises a signal-burst generated at said higher frequency, said measure of emissions is performed while sweeping said second time-varying field and while said signal-burst is transmitted by an interrogation field generating coil, and said plurality of higher-order harmonic amplitudes so measured are for harmonics selected from a range of 2 to 100 times a fundamental resonant frequency for said sensor element.

20. An apparatus for monitoring a corrosive, comprising:

a sensor element made of a magnetically soft material operatively arranged within a first and second time-varying interrogation magnetic field, said first time-varying magnetic field being generated at a frequency higher than that for said second magnetic field;

a receiver, remote from said sensor element, to measure intensity of electromagnetic emissions from said sensor element to identify a relative maximum amplitude value for each of a plurality of higher-order harmonic frequency amplitudes so measured; and

a unit to determine a value for corrosion in proximity to said sensor element using said relative maximum harmonic amplitude values identified.

21. The apparatus of claim 20 wherein said higher frequency of said first field is at least ten times greater than said second magnetic field frequency;

said unit comprises a processor, said magnetically soft material comprises a ferromagnetic alloy, and a pre-correlation made for a calibration sensor element of like size and material characteristics of said sensor element is used to determine said corrosion value.

22. The apparatus of claim 20 wherein said higher frequency of said first field is selected from a first range of frequencies from 50 Hz to 10 MHz and said frequency of said second field is selected from a second range of frequencies from 0.1 Hz to 10 Hz;

and further comprising a computerized device for instructing said receiver to take, over a time interval, a series of sensor element emission measurements to produce a corrosion response profile comprising a series of corresponding corrosion values for said series of emission measurements taken.

23. The apparatus of claim 20 wherein:

said sensor element is located within an analyte;

a pre-correlation made between a series of comparative relative maximum harmonic amplitude values, represented by a plurality voltages corresponding to certain of said emission intensity measurements taken, and a corresponding series of values representing concentration of the corrosive is used to determine said corrosion value.

24. The apparatus of claim 20 wherein the sensor element is made of a ferromagnetic alloy, is elongated, and is located within a solid analyte, and said value for corrosion represents a localized concentration of the corrosive within said solid analyte.

25. The apparatus of claim 20 wherein:

said sensor element is located within a solid analyte, said solid analyte comprises a component of a material selected from the group consisting of concrete, mortar, tar, wood, fiberboard, particleboard, plasterboard, sheetrock, fiberglass, plexiglass, resins, and plastics;

said plurality of higher-order harmonic amplitudes so measured are for harmonics selected from a range of 2 to 100 times a fundamental resonant frequency for said sensor element; and

said receiver comprises an electromagnetic pick-up coil.

26. The apparatus of claim 20 wherein said sensor element is at least partially encapsulated within a corrosion-resistant casing;

and further comprising a magnetically hard element supporting a biasing field adjacent said magnetically soft sensor element, said magnetically hard element comprised of a material chemically responsive to a fluid analyte such that exposure thereto causes a change in said biasing field.

27. The apparatus of claim 20 wherein the sensor element is located on a surface of a solid analyte, said value for corrosion represents a localized surface degradation of said solid analyte, and said solid analyte comprises a component of a material selected from the group consisting of concrete, mortar, tar, wood, fiberboard, particleboard, plasterboard, sheetrock, fiberglass, plexiglass, resins, and plastics.