Wireless monitoring of temperature

• US 6,208,253 B1
• Filed: 04/12/2000
• Issued: 03/27/2001
• Est. Priority Date: 04/12/2000
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Gershenfeld, Neil, Fletcher, Richard
• Primary Examiner(s): Lee, Benjamin C.
• Application Number:
  US09/548,079
• Time in Patent Office: 349 Days
• Field of Search: 340/572.1, 340/572.6, 340/584, 340/870.17, 340/10.1, 374/100, 374/141, 324/200, 324/201, 324/224
• US Class Current: 340/584
• CPC Class Codes: G01K 7/38 the variations of temperature influencing the magnetic permeability

Abstract

Temperature sensing through observable, temperature-dependent effects on an interrogating magnetic field is facilitating by a sensing module having, first, a signal element that interacts with the interrogation field to produce a remotely readable magnetic response; and disposed proximate to the signal element, a temperature-sensitive component. This latter component may include a modulation element having a magnetic permeability varying with temperature in the operating range and/or a bias element comprising a magnet having a Curie temperature in the operating range. The temperature-sensitive component interacts magnetically with the signal element such that the remotely readable magnetic response is indicative of a temperature in the operating range.

Claims

1. A temperature sensor for determining temperature within an operating range, the sensor comprising:

a. a signal element for producing a remotely readable magnetic response;

b. disposed proximate to the signal element, a temperature-sensitive component comprising at least one of (i) a modulation element having a magnetic permeability varying with temperature in the operating range, and (ii) a bias element comprising a magnet having a Curie temperature in the operating range,

wherein

c. the temperature-sensitive component interacts magnetically with the signal element whereby the remotely readable magnetic response is indicative of a temperature in the operating range.

2. The sensor of claim 1 wherein the signal element comprises a material producing detectable harmonics in response to an interrogation field and the temperature-sensitive component is a magnet having a Curie temperature in the operating range, the magnet producing, below the Curie temperature, a local magnetic field affecting the signal element and of sufficient magnitude to suppress the harmonics.

3. The sensor of claim 1 wherein the signal element comprises a magnetomechanical material and the temperature-sensitive component is a magnet having a Curie temperature in the operating range, the sensor exhibiting a detectable resonance in response to an interrogation field below the Curie temperature.

4. The sensor of claim 1 wherein the signal element comprises a material producing detectable harmonics in response to an interrogation field and the temperature-sensitive component is a modulation element having a temperature-variable magnetic permeability and a Curie point within the operating range, the modulation element attenuating the harmonics below the Curie point.

5. The sensor of claim 1 wherein the signal element comprises a material producing detectable harmonics in response to an interrogation field and the temperature-sensitive component comprises (i) a modulation element having a variable magnetic permeability and a Curie point within the operating range, the permeability varying with temperature in the operating range, and (ii) a bias element comprising a magnet producing a local magnetic field affecting the signal element and of sufficient magnitude within the operating range to suppress the harmonics, the modulation and bias elements interacting such that, at temperatures within the operating range but above the Curie point, the bias element suppresses the harmonics.

6. The sensor of claim 5 wherein the signal element comprises first and second opposed surfaces, the temperature-sensitive component being disposed adjacent to the first surface.

7. The sensor of claim 6 wherein the modulation element is disposed between the signal element and the bias element.

8. The sensor of claim 6 wherein the bias element is disposed between the signal element and the modulation element.

9. The sensor of claim 1 wherein the signal element comprises a magnetomechanical material and the temperature-sensitive component comprises (i) a modulation element having a magnetic permeability varying with temperature in the operating range, and (ii) a bias element comprising a magnet producing a local magnetic field determining a resonant frequency of the signal element, the permeability of the modulation element shunting a portion of the local magnetic field from the signal element and thereby altering the resonant frequency in a temperature-dependent fashion within the operating range.

10. The sensor of claim 9 wherein the signal element comprises first and second opposed surfaces, the temperature-sensitive component being disposed adjacent to the first surface.

11. The sensor of claim 9 wherein the modulation element is disposed between the signal element and the bias element.

12. The sensor of claim 9 wherein the bias element is disposed between the signal element and the modulation element.

13. A method of sensing temperature within an operating range, the method comprising the steps of:

a. providing a sensor comprising a signal element for producing a remotely readable magnetic response and, disposed proximate to the signal element, a temperature-sensitive component comprising at least one of (i) a modulation element having a magnetic permeability varying with temperature in the operating range, and (ii) a bias element comprising a magnet having a Curie temperature in the operating range;

b. subjecting the sensor to a magnetic interrogation field, the temperature-sensitive component interacting magnetically with the signal element to affect the interrogation field in a manner indicative of a temperature in the operating range; and

c. sensing the effect on the interrogation field.

14. The method of claim 13 wherein the signal element comprises a material producing detectable harmonics in response to the interrogation field and the temperature-sensitive component is a magnet having a Curie temperature in the operating range, the magnet producing, below the Curie temperature, a local magnetic field affecting the signal element and of sufficient magnitude to detectably suppress the harmonics.

15. The method of claim 13 wherein the signal element comprises a magnetomechanical material and the temperature-sensitive component is a magnet having a Curie temperature in the operating range, the interrogation field eliciting a detectable resonance below the Curie temperature.

16. The method of claim 13 wherein the signal element comprises a material producing detectable harmonics in response to the interrogation field and the temperature-sensitive component is a modulation element having a temperature-variable magnetic permeability and a Curie point within the operating range, the modulation element detectably attenuating the harmonics below the Curie point.

17. The method of claim 13 wherein the signal element comprises a material producing detectable harmonics in response to the interrogation field and the temperature-sensitive component comprises (i) a modulation element having a variable magnetic permeability and a Curie point within the operating range, the permeability varying with temperature in the operating range, and (ii) a bias element comprising a magnet producing a local magnetic field affecting the signal element and of sufficient magnitude within the operating range to suppress the harmonics, the modulation and bias elements interacting such that, at temperatures within the operating range but above the Curie point, the bias element detectably suppresses the harmonics.

18. The method of claim 13 wherein the signal element comprises a magnetomechanical material and the temperature-sensitive component comprises (i) a modulation element having a magnetic permeability varying with temperature in the operating range, and (ii) a bias element comprising a magnet producing a local magnetic field determining a resonant frequency of the signal element, the permeability of the modulation element shunting a portion of the local magnetic field from the signal element and thereby altering the resonant frequency in a temperature-dependent fashion within the operating range.

19. The method of claim 13 further comprising the step of relating the temperature to a temperature-dependent parameter to determine a magnitude of the parameter.