Systems and methods for remote sensing using inductively coupled transducers

• US 7,456,744 B2
• Filed: 05/16/2006
• Issued: 11/25/2008
• Est. Priority Date: 05/16/2006
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Free, M. Benton, Kuhns, David W.
• Primary Examiner(s): Nguyen; Tai T
• Application Number:
  US11/383,640
• Publication Number:
  US 20080012579A1
• Time in Patent Office: 924 Days
• Field of Search: 340/572.1, 340/572.2, 340/572.5, 340/572.7, 340/568.1, 340/568.2, 340/604, 340/605
• US Class Current: 340/572.1
• CPC Class Codes: G06K 19/0716 at least one of the integrated circuit chips comprising a sensor or an interface to a sensor
• CPC Class Codes: G06K 19/0717 the sensor being capable of sensing environmental conditions such as temperature history or pressure
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card

Abstract

A remote sensing device includes a sensor and reference circuit. A resonant circuit of the sensor has a resonant characteristic modifiable by exposure to an external condition. The sensor is configured to produce a sensor signal associated with the modifiable resonant characteristic. A reference circuit of the remote sensing device is configured to produce a reference signal suitable for use in conjunction with the sensor signal. The reference signal is used to account for variations of the sensor signal due to variations in the inductive coupling between the remote sensing device and a reader designed to detect the reference signal and the sensor signal.

Claims

1. A remote sensing device comprising:

a sensor having a resonant characteristic modifiable by exposure to an external condition, comprising a resonant electrical circuit configured to produce a sensor signal associated with the modifiable resonant characteristic; and

a reference circuit having a reference resonant characteristic, the reference circuit configured to produce a reference signal suitable for use in conjunction with the sensor signal to account for variations of the sensor signal due to changes in inductive coupling between the remote sensing device and a reader configured to detect the reference signal and the sensor signal.

2. The device of claim 1, wherein the external condition comprises an environmental condition.

3. The device of claim 1, wherein the external condition comprises moisture.

4. The device of claim 1, wherein the external condition comprises humidity.

5. The device of claim 1, wherein exposure to the external condition alters a material property of the sensor.

6. The device of claim 1, wherein the modifiable resonant characteristic comprises at least one of resonant frequency, Q factor, bandwidth, and frequency response characteristic.

7. The device of claim 1, wherein the changes in inductive coupling between the remote sensing device and the reader are due to changes in at least one of alignment and distance of the sensing device relative to the reader.

8. The device of claim 1, wherein the changes in inductive coupling are due to electromagnetic interference.

9. The device of claim 1, wherein the changes in inductive coupling are due to changes in conditions experienced by both the sensing device and the reference circuit.

10. The device of claim 1, wherein the reference signal is suitable for use in conjunction with the sensor signal to account for the variations in at least one of alignment and positioning based on changes in at least one of amplitude, kurtosis, peak width, frequency, skew, and curve fit of the sensor signal relative to the reference signal.

11. The device of claim 1, wherein the reference signal is suitable for normalizing the sensor signal.

12. The device of claim 1, wherein the reference signal is suitable for correcting the sensor signal.

13. A remote sensing system, comprising:

a sensing device, comprising;

a sensor circuit having a resonant characteristic modifiable by exposure to an external condition, comprising a resonant electrical circuit configured to produce a sensor signal associated with the modifiable resonant characteristic; and

a reference circuit having a reference resonant characteristic, the reference circuit configured to produce a reference signal; and

a receiver configured to receive the sensor signal and the reference signal and to use the reference signal to account for variations in the sensor signal due to changes in inductive coupling between the sensing device and the receiver.

14. The remote sensing system of claim 13, wherein the receiver is configured to account for the variations based on changes in amplitude of the sensor signal relative to the reference signal.

15. The remote sensing system of claim 13, wherein the receiver is configured to account for the variations based on changes in shape of the sensor signal relative to the reference signal.

16. The remote sensing system of claim 13, wherein the receiver is configured to account for the variations based on at least one of changes in amplitude, kurtosis, peak width, frequency, skew, and curve fit of the sensor signal relative to the reference signal.

17. The remote sensing signal of claim 13, wherein the receiver is further configured to detect a change in the external condition based on a change in the sensor signal.

18. The remote sensing system of claim 17, wherein the receiver is further configured to produce an alarm signal based on the change in the external condition.

19. The remote sensing system of claim 13, wherein the sensor circuit comprises at least a capacitor and an inductor and the resonant frequency of the sensor circuit is modifiable based on changes in capacitance of the capacitor.

20. The remote sensing system of claim 13, wherein the sensor circuit comprises at least a capacitor and an inductor and the resonant frequency of the sensor circuit is modifiable based on changes in the inductance of the inductor.

21. The remote sensing system of claim 13, wherein the resonant frequency of the sensor circuit is modifiable based on a dimensional change of at least one circuit element of the sensor circuit.

22. The remote sensing system of claim 13, wherein the resonant frequency of the sensor circuit is modifiable based on a change in an electrical property of at least one circuit element of the sensor circuit.

23. The remote sensing system of claim 13, wherein the receiver is configured to normalize the sensor signal based on the reference signal.

24. The remote sensing system of claim 13, where the receiver is configured to use the reference signal to correct the sensor signal.

25. The remote sensing system of claim 13, wherein the sensor circuit is configured to be exposed to the external condition and the reference circuit is configured to be protected from the external condition.

26. The remote sensing system of claim 13, wherein the sensor circuit has a relatively higher sensitivity to the external condition than the reference circuit.

27. A method, comprising:

receiving, by a receiving device, a sensor signal produced by a sensor circuit of a sensing device, the sensor circuit having a resonant frequency modifiable by exposure to an external condition;

receiving, by the receiving device, a reference signal produced by a reference circuit of the sensing device, the reference circuit having a reference resonant characteristic;

processing the sensor signal in conjunction with the reference signal to account for variations inductive coupling between the sensing device and the receiving device; and

determining changes in the external condition using the processed signal.

28. The method of claim 27, wherein processing the sensor signal in conjunction with the reference signal comprises processing based on a change in at least one of amplitude, kurtosis, peak width, frequency, skew, and curve fit of the sensor signal relative to the reference signal.

29. The method of claim 27, wherein the external condition comprises an environmental condition.

30. The method of claim 27, wherein processing the sensor signal comprises normalizing the sensor signal using the reference signal.

31. The method of claim 27, wherein processing the sensor signal comprises correcting the sensor signal using the reference signal.

32. The method of claim 27, further comprising generating an alarm based on the changes in the external condition.

33. A remote sensing system, comprising:

a sensing device, comprising;

a sensor circuit having a resonant characteristic modifiable by exposure to an external condition, comprising a resonant electrical circuit configured to produce a sensor signal associated with the modifiable resonant characteristic; and

a reference circuit having a reference resonant characteristic, the reference circuit configured to produce a reference signal; and

means for processing the sensor signal in conjunction with the reference signal to account for variations in at least one of alignment and position of the sensing device relative to the receiving device; and

means for determining changes in the external condition using the processed signal.

34. The system of claim 33, further comprising means for processing the sensor signal in conjunction with the reference signal based on a change in at least one of amplitude, kurtosis, peak width, frequency, skew, and curve fit of the sensor signal relative to the reference signal.

35. The system of claim 33, further comprising means for normalizing the sensor signal based on the reference signal.

36. The system of claim 33, further comprising means for correcting the sensor signal using the reference signal.