INDUCTIVE SENSOR

• US 20080018424A1
• Filed: 07/10/2006
• Published: 01/24/2008
• Est. Priority Date: 07/10/2006
• Status: Abandoned Application

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Takahata, Kenichi
• Application Number:
  US11/456,410
• Publication Number:
  US 20080018424A1
• Time in Patent Office: Days
• US Class Current: 336/20
• CPC Class Codes: H01F 21/005 Inductances without magnetic core
• CPC Class Codes: H01F 21/02 continuously variable, e.g. variometers

Abstract

An inductive sensor includes an inductor having one or more loops and a sensor material configured to respond to a parameter of interest by a dimensional change of the sensor material. The sensor material is oriented within the loops of the inductor so that the dimensional change of the sensor material produces a dimensional change of the inductor. The dimensional change of the inductor alters the inductance of the inductor.

Claims

1. An inductive sensor, comprising:

an inductor comprising one or more loops and associated with an inductance; and

a sensor material configured to respond to a parameter of interest by a dimensional change of the sensor material, the sensor material oriented within the loops of the inductor so that the dimensional change of the sensor material produces a dimensional change of the inductor, the dimensional change of the inductor altering the inductance of the inductor.

2. The sensor of claim 1, wherein the sensor material is oriented so that the dimensional change of the sensor material causes a change in cross sectional area of the inductor.

3. The sensor of claim 1, wherein the sensor material is oriented so that the dimensional change of the sensor material causes a change in length of the inductor.

4. The sensor of claim 1, wherein the sensor material is oriented so that the dimensional change of the sensor material causes a change in distance between two or more loops of the inductor.

5. The sensor of claim 1, wherein the sensor material is disposed between at least two loops of the inductor and the dimensional change of the sensor material causes a change in a distance between the at least two loops.

6. The sensor of claim 1, wherein the sensor material is disposed between at least two loops of the inductor and the dimensional change of the sensor material causes a change in an angle between the at least two loops.

7. The sensor of claim 1, wherein the sensor material comprises a polymer capable of expanding or contracting in response to a change in the parameter of interest.

8. The sensor of claim 1, wherein the sensor material comprises a hydrogel.

9. The sensor of claim 1, wherein the parameter of interest comprises at least one of temperature, moisture, pH, fluid flow, salinity, solvent composition, glucose concentration, electric field, light, and ion concentration.

10. The sensor of claim 1, further comprising a capacitor electrically coupled to the inductor to form a resonant circuit, wherein a change in the parameter of interest causes a change in a resonance characteristic of the resonant circuit.

11. The sensor of claim 1, wherein the capacitor comprises a segmented electrode.

12. The sensor of claim 1, wherein at least one of the loops is disposed on a flexible substrate.

13. The sensor of claim 12, wherein the dimensional change of the inductor involves flexure of the flexible substrate and the at least one loop.

14. The sensor of claim 12, further comprising a capacitor having a capacitive having a capacitive electrode formed on the flexible substrate and within at least one loop, the capacitor electrically coupled to the inductor to form a resonant circuit.

15. The sensor of claim 1, further comprising a latching mechanism configured to initially orient at least one loop with respect to at least another loop.

16. A sensor system comprising:

an inductive sensor, comprising;

an inductor comprising one or more loops;

a sensor material configured to respond to a parameter of interest by a dimensional change of the sensor material, the sensor material oriented within a region defined by the loops of the inductor so that the dimensional change of the sensor material produces a dimensional change of the inductor causing a change in inductance of the inductor; and

sensor circuitry electrically coupled to the inductor to form a resonant circuit having a resonant characteristic dependent on the inductance; and

an interrogator configured to detect a change in the resonance characteristic of the resonant circuit and to analyze the parameter of interest based on the resonance characteristic.

17. The sensor system of claim 16, wherein the interrogator is wirelessly coupled to the inductive sensor.

18. The sensor system of claim 16, wherein the resonance characteristic comprises resonant frequency.

19. The sensor system of claim 16, further comprising a reference circuit configured to produce a reference signal detectable by the interrogator, wherein the interrogator is configured to use the reference signal to correct for errors in a signal produced by the inductive sensor.

20. The sensor system of claim 16, wherein:

the inductive sensor is disposed in or on a moisture absorptive dressing configured to be placed on a patient;

the parameter of interest comprises moisture; and

the interrogator is configured to detect moisture in the dressing based on the resonance characteristics of the inductive sensor.