Radiofrequency based sensor arrangement and a method

• US 7,714,593 B2
• Filed: 12/16/2004
• Issued: 05/11/2010
• Est. Priority Date: 12/18/2003
• Status: Active Grant

• Current Assignee: SMARTRAC Investment B.V. (Avery Dennison Corporation)
• Original Assignee: Upm-Kymmene Corporation
• Inventors: Varpula, Timo, Saari, Juha-Matti, Seppa, Heikki
• Primary Examiner(s): Dole; Timothy J
• Assistant Examiner(s): Baldridge; Benjamin M
• Application Number:
  US10/583,381
• Publication Number:
  US 20070241762A1
• Time in Patent Office: 1,972 Days
• Field of Search: 324/654, 436/121
• US Class Current: 324/654
• CPC Class Codes: G06K 19/0717 the sensor being capable of sensing environmental conditions such as temperature history or pressure
• CPC Class Codes: G08C 17/04 using magnetically coupled devices
• CPC Class Codes: G08C 17/06 using capacity coupling
• CPC Class Codes: Y10T 436/184 Only hydrogen sulfide

Abstract

A sensor arrangement for a sensor arrangement remotely readable by radio frequencies. The sensor arrangement includes an LC resonator that includes a capacitor and a coil, and a sensor element coupled to the LC resonator whose properties change as a function of a measurable quantity. A sensor element according to the invention does not form a direct galvanic contact with the LC resonator, rather the coupling is implemented capacitively or inductively.

Claims

1. A sensor arrangement remotely readable by a separate reader utilizing radio frequencies for determining desired quantities from sources, the arrangement comprising:

an LC resonator comprising a capacitor and a coil,

an electrically conductive ring,

a sensor element coupled to the LC resonator, whose properties change as a function of a measurable quantity, the sensor element being coupled inductively with the LC resonator without forming a direct galvanic contact, wherein the sensor element is arranged inside the electrically conductive ring and is thinner than the electrically conductive ring, and

a package containing foodstuffs or medicinal substances, wherein the sensor element is arranged inside the package and the coil is arranged outside the package,

wherein the coil is configured to generate a magnetic field on a location of the sensor element, and wherein the sensor element directly affects the magnetic field generated by the coil.

2. The sensor arrangement according to claim 1, wherein the sensor element is cumulatively variable.

3. The sensor arrangement according to claim 1, wherein the sensor arrangement is suitable for use in monitoring deterioration of foodstuffs and medicinal substances.

4. The sensor arrangement according to claim 1, wherein the ring is circular, oval or polygonal in shape.

5. An apparatus for indicating a deterioration event, said apparatus comprising:

a sensor element capable of reacting with a compound generated by the deterioration event, or capable of reacting with oxygen,

an LC resonator comprising a capacitor and a coil, wherein said coil is arranged to induce eddy currents in said sensor element by an alternating magnetic field generated by said coil, said eddy currents induce a voltage in said coil such that said voltage is dependent on electrical conductivity and thickness of said sensor element, and

an electrically conductive ring having a thickness greater that the sensor element, wherein said sensor element is disposed inside the electrically conductive ring.

6. The apparatus according to claim 5, wherein said sensor element is sensitive to hydrogen sulfide.

7. The apparatus according to claim 5, wherein a frequency of an alternating current coupled to said coil is variable in order to determine a resonance frequency of said coil.

8. The apparatus according to claim 5, further comprising:

a package, wherein said sensor element is located inside the package, and said coil is located outside the package.

9. The apparatus according to claim 8, wherein a perishable product selected from a group consisting of foodstuff and a medicinal substance is arranged inside the package.

10. The apparatus according to claim 5, wherein said sensor comprises a metal selected from a group consisting of silver and copper.

11. The apparatus according to claim 5, wherein said ring comprises aluminum.

12. A method for indicating a deterioration event by using a sensor element and an LC resonator, said LC resonator comprising a capacitor and coil, said method comprising:

arranging the sensor element inside a package containing a perishable product, said sensor element being capable of reacting with a compound generated by deterioration of said perishable product, or capable of reacting with oxygen,

generating an alternating magnetic field by said coil, inducing eddy currents in said sensor element by said alternating magnetic field, and

inducing a voltage in said coil by said eddy currents, wherein said voltage depends on an electrical conductivity and a thickness of said sensor element, and wherein said sensor element is arranged inside an electrically conductive ring that is thicker than said sensor element.

13. The method according to claim 12, wherein said sensor element is sensitive to hydrogen sulfide.

14. The method according to claim 12, further comprising

changing a frequency of an alternating current coupled to said coil in order to determine a resonance frequency of said coil.

15. The method according to claim 14, further comprising:

determining a distance between said sensor element and said coil based on the measured changes in the resonance frequency of said coil.

16. The method according to claim 12, wherein said coil is located outside the package.

17. The method according to claim 16, wherein said perishable product is selected from a group consisting of foodstuff and a medicinal substance.

18. The method according to claim 12, wherein said sensor comprises a metal selected from a group consisting of silver and copper.

19. The method according to claim 12, wherein said ring comprises aluminum.