Resonant sensor system and method

• US 5,942,991 A
• Filed: 06/06/1995
• Issued: 08/24/1999
• Est. Priority Date: 06/06/1995
• Status: Expired due to Term

• Current Assignee: Diversified Technologies Incorporated (Henkel AG & Co KGaA)
• Original Assignee: Diversified Technologies Incorporated (Henkel AG & Co KGaA)
• Inventors: Weisenseel, Robert A., Gaudreau, Marcel P. J.
• Primary Examiner(s): Horabik, Michael
• Assistant Examiner(s): Edwards, Jr., Timothy
• Application Number:
  US08/466,374
• Time in Patent Office: 1,540 Days
• Field of Search: 340/870.16, 340/870.28, 340/870.29, 340/870.3, 340/870.31, 340/505, 340/825.54, 340/870.01, 340/870.18, 340/601, 340/690, 340/547, 324/334, 324/337, 342/22
• US Class Current: 340/870.16
• CPC Class Codes: G06K 19/0717 the sensor being capable of sensing environmental conditions such as temperature history or pressure

Abstract

Apparatus, and related method, for remotely measuring at 1east one environmental condition includes an electromagnetically resonant sensor having a measurable resonance characteristic (e.g., center resonance frequency, quality factor, or bandwidth) that varies in correspondence to changes in the environmental condition present at the sensor. The sensor emits an electromagnetic return signal representative of a state of the resonance characteristic when an electromagnetic excitation signal impinges on the sensor. The electromagnetic excitation signal is generated by a generator located separate and away from the sensor, and the excitation signal is then directed at the remote sensor. The sensor thus remotely detects and measures the environmental condition. In one embodiment, the sensor is an electromagnetically resonant electrical circuit. In another embodiment, the sensor is an antenna resonator (e.g., a half-wavelength antenna) made of a conductive material.

Claims

1. Apparatus for remotely measuring at least one environmental condition, comprising:

an electromagnetically resonant sensor having a resonance frequency which varies as a result of at least one physical change to the sensor, the at least one physical change being due to one or more changes in the at least one environmental condition, the sensor emitting an electromagnetic return signal having a frequency at or near the resonance frequency when an electromagnetic excitation signal having a frequency at or near the resonance frequency impinges on the sensors; and

an electromagnetic excitation signal generator which is separated from the sensor and located away from the sensors and which generates the electromagnetic excitation signal having the frequency at or near the resonance frequency.

2. The apparatus of claim 1 wherein the sensor comprises an antenna resonator made of a conductive material.

3. The apparatus of claim 1 further comprising at least two receivers for receiving the electromagnetic return signal, the receivers being separate from the sensor, located away from the sensor, and located a distance away from each other.

4. The apparatus of claim 1 wherein the sensor comprises an electromagnetically resonant electrical circuit.

5. The apparatus of claim 4 wherein the electromagnetically resonant electrical circuit comprises a capacitance and an inductance.

6. The apparatus of claim 5 wherein the circuit comprises a substrate having two opposing surfaces, one surface having a first capacitor plate and an inductor thereon and the other surface having a second capacitor plate thereon.

7. Apparatus for remotely measuring an environmental condition, comprising:

an electromagnetically resonant senor having a resonance frequency which varies as a result of at least one physical change to the sensor, the at least one physical change being due to one or more changes in the environmental condition;

a generator, separate from the sensor and located remote from the sensor, for generating at least one electromagnetic excitation signal having a frequency at or near the resonance frequency; and

a monitor, separate from the sensor and located remote from the sensor, for detecting at least one electromagnetic return signal returned by the sensor in response to the at least one electromagnetic excitation signal, the at least one electromagnetic return signal having a frequency at or near the resonance frequency.

8. The apparatus of claim 7 wherein the sensor comprises an antenna resonator made of a conductive material.

9. The apparatus of claim 7 further comprising at least two of the monitors, the monitors being located a distance away from each other.

10. The apparatus of claim 8 wherein the sensor comprises an electromagnetically resonant electrical circuit.

11. The apparatus of claim 10 wherein the electromagnetically resonant electrical circuit comprises a capacitance and an inductance.

12. The apparatus of claim 11 wherein the circuit comprises a substrate having two opposing surfaces, one surface having a first capacitor plate and an inductor thereon and the other surface having a second capacitor plate thereon.

13. A method of remotely measuring an environmental condition, comprising:

providing an electromagnetically resonant sensor at a first location, the sensor having a resonance frequency which varies as a result of at least one physical change to the sensor, the at least one physical change being due to one or more changes in the environmental condition;

generating at least one electromagnetic excitation signal with an electromagnetic signal generator which is separate from the sensor and disposed at a second location remote from the first location, the at least one electromagnetic excitation signal having a frequency at or near the resonance frequency; and

monitoring for at least one electromagnetic return signals returned by the sensor in response to the at least one electromagnetic excitation signal, the at least one electromagnetic return signal having a frequency at or near the resonance frequency.

14. The method of claim 13 wherein the step of providing the electromagnetically resonant sensor comprises providing an antenna resonator made of a conductive material.

15. The method of claim 13 further comprising, after the step of generating the at least one electromagnetic excitation signal, directing the at least one electromagnetic excitation signal from the second location to the first location such that the at least one electromagnetic excitation signal impinges on the sensor.

16. The method of claim 13 wherein the step of monitoring further comprises monitoring from two separate locations, both of which are located away from the first location and located a distance away from each other.

17. The method of claim 13 wherein the step of providing the electromagnetically resonant sensor comprises providing an electromagnetically resonant electrical circuit.

18. The method of claim 17 wherein the step of providing the electromagnetically resonant electrical circuit comprises providing a capacitance and an inductance.

19. The method of claim 18 wherein the step of providing the capacitance and the inductance comprises providing a substrate having two opposing surfaces, one surface having a first capacitor plate and an inductor thereon and the other surface having a second capacitor plate thereon.