METHOD AND SYSTEM FOR MONITORING ENVIRONMENTAL CONDITIONS

• US 20070024410A1
• Filed: 05/13/2006
• Published: 02/01/2007
• Est. Priority Date: 05/13/2005
• Status: Active Grant

• Current Assignee: Bellutech LLC
• Original Assignee: Evigia Systems, Inc.
• Inventors: Yazdi, Navid
• Granted Patent: US 7,619,346 B2
• Time in Patent Office: Days
• US Class Current: 338/13
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G01K 1/045 temperature indication combined with the indication of another variable indicating of human comfort G01W1/17
• CPC Class Codes: G01K 3/04 in respect of time

Abstract

A sensing system, sensing method, and method of producing a sensing system capable of providing a cumulative measurement capability, such as in the form of a RFID tag capable of measuring cumulative heat and humidity for continuous monitoring of storage and shipping conditions of various goods. The system includes integrated circuitry and a plurality of sensing elements, preferably having cantilevered bimorph beams. Each sensing element is responsive to an environmental condition so as to deflect toward and away from open contacts in response to changes in the environmental condition. Each sensing element produces a digital output when it contacts and closes its open contacts. The integrated circuitry interfaces with the sensing elements so that the digital outputs of the sensing elements are processed to generate a system output of the sensing system.

Claims

1. A micro-electro-mechanical digital sensing system comprising:

a plurality of sensing elements on a substrate, each sensing element comprising a cantilevered bimorph beam and at least one set of open contacts configured for non-latching contact-mode operation with the bimorph beam, the bimorph beam of each sensing element being responsive to changes in an environmental condition so as to deflect toward and away from the open contacts thereof in response to the changes in the environmental condition, the bimorph beams being configured to contact and close their respective open contacts at different levels of the environmental condition, each of the sensing elements producing a digital output when the bimorph beam thereof contacts and closes the open contacts thereof; and

an integrated circuitry interfacing with the sensing elements so that the digital outputs of the sensing elements are processed to generate a system output of the sensing system.

2. The micro-electro-mechanical digital sensing system according to claim 1, wherein the environmental condition to which the bimorph beams are responsive is at least one environmental condition chosen from the group consisting of temperature, relative humidity, chemicals, shock/vibration, tilt, pressure, acceleration, and biological agents.

3. The micro-electro-mechanical digital sensing system according to claim 1, further comprising means for resistively or capacitively sensing contact between the bimorph beams and their respective open contacts.

4. The micro-electro-mechanical digital sensing system according to claim 1, wherein the integrated circuitry comprises front-end circuitry that directly interfaces with the sensing elements and detects contacts between the bimorph beams and their respective open contacts.

5. The micro-electro-mechanical digital sensing system according to claim 1, wherein the integrated circuitry is configured to generate the system output by individually processing the digital outputs of the sensing elements that at a given time contact and close their respective open contacts in response to a maximum level of the environmental condition at the given time.

6. The micro-electro-mechanical digital sensing system according to claim 1, the integrated circuitry is configured to generate the system output as a time-weighted cumulative output generated on the basis of the digital outputs of the sensing elements over time.

7. The micro-electro-mechanical digital sensing system according to claim 6, further comprising at least one clock that generates at least one clock speed, and the integrated circuitry uses the clock speed to generate the time-weighted cumulative output.

8. The micro-electro-mechanical digital sensing system according to claim 7, wherein the integrated circuitry is configured to generate the time-weighted cumulative output by individually processing the digital outputs of the sensing elements that at a given time contact and close their respective open contacts in response to a maximum level of the environmental condition at the given time, and is further configured to integrate the digital outputs over time using the clock speed of the clock without use of an arithmetic logic unit.

9. The micro-electro-mechanical digital sensing system according to claim 1, further comprising at least one clock that generates multiple different clock speeds that are assigned to the digital outputs of the sensing elements to generate the system output.

10. The micro-electro-mechanical digital sensing system according to claim 9, wherein the integrated circuitry is configured to associate higher clock speeds with the digital outputs of the sensing elements responsive to higher levels of the environmental condition.

11. The micro-electro-mechanical digital sensing system according to claim 1, wherein the integrated circuitry communicates with a subset of the sensing elements, the digital outputs of only the subset of sensing elements are processed by the integrated circuitry to generate the system output of the sensing system, and a remainder of the sensing elements not part of the subset of sensing elements are responsive to levels of the environmental condition outside a range defined by the levels of the environmental condition to which the subset of sensing elements are responsive.

12. The micro-electro-mechanical digital sensing system according to claim 1, wherein the bimorph beams of a first set of the sensing elements are responsive to temperature and the bimorph beams of a second set of the sensing elements are responsive to relative humidity.

13. The micro-electro-mechanical digital sensing system according to claim 12, further comprising means for temperature compensation of the second set of sensing elements.

14. The micro-electro-mechanical digital sensing system according to claim 13, wherein the temperature compensation means comprises temperature switches electrically connected to the second set of sensing elements.

15. The micro-electro-mechanical digital sensing system according to claim 14, wherein each of the temperature switches comprises a cantilevered bimorph beam between at least two sets of open contacts, the bimorph beams of the temperature switches being responsive to temperature.

16. The micro-electro-mechanical digital sensing system according to claim 14, wherein the temperature switches are electrically connected to the second set of sensing elements in series and in shunt configurations.

17. The micro-electro-mechanical digital sensing system according to claim 14, wherein the second set of sensing elements comprises subsets of the sensing elements connected in parallel, each subset defines a humidity switch, and each of the sensing elements within each humidity switch is electrically connected to a corresponding one of the temperature switches.

18. The micro-electro-mechanical digital sensing system according to claim 17, wherein the sensing elements within each humidity switch are configured to contact and close their respective open contacts at different levels of relative humidity.

19. The micro-electro-mechanical digital sensing system according to claim 18, wherein the sensing elements and the temperature switches within each humidity switch cooperate to yield a single digital signal over a limited temperature range determined by the temperature switches.

20. The micro-electro-mechanical digital sensing system according to claim 19, wherein the temperature switches are electrically connected to their respective sensing elements in series and in shunt configurations.

21. The micro-electro-mechanical digital sensing system according to claim 1, further comprising a battery for powering the integrated circuitry.

22. The micro-electro-mechanical digital sensing system according to claim 1, further comprising a radio frequency identification link operable to wirelessly transmit the system output.

23. The micro-electro-mechanical digital sensing system according to claim 1, wherein the bimorph beams of the sensing elements are responsive to the changes in the environmental condition without any power supplied to the bimorph beams.

24. The micro-electro-mechanical digital sensing system according to claim 1, wherein the integrated circuitry generates the system output as a digital system output directly from the digital outputs of the sensing elements without performing any analog-to-digital conversion.

25. A method of sensing an environmental condition, the method comprising the steps of:

providing a sensing system comprising integrated circuitry and a plurality of contact-mode sensing elements, the sensing elements being responsive to the environmental condition and being operable to close at least one pair of open contacts at different levels of the environmental condition to individually produce digital outputs; and

interfacing the sensing elements with the integrated circuitry so that the digital outputs of the sensing elements are processed to generate a system output of the sensing system.

26. The method according to claim 25, wherein the environmental condition is at least one environmental condition chosen from the group consisting of temperature, relative humidity, chemicals, shock/vibration, tilt, pressure, acceleration, and biological agents.

27. The method according to claim 25, wherein the integrated circuitry generates the system output by individually processing the digital outputs of the sensing elements that at a given time contact and close their respective open contacts in response to a maximum level of the environmental condition at the given time.

28. The method according to claim 25, wherein at least some of the sensing elements are responsive to temperature and at least some of the sensing elements are responsive to relative humidity.

29. The method according to claim 25, wherein the integrated circuitry generates the system output as a time-weighted cumulative output generated on the basis of the digital outputs of the sensing elements over time.

30. The method according to claim 29, wherein the sensing system comprises at least one clock that generates at least one clock speed, and the integrated circuitry uses the clock speed to generate the time-weighted cumulative output.

31. The method according to claim 30, wherein the integrated circuitry generates the time-weighted cumulative output by individually processing the digital outputs of the sensing elements that at a given time contact and close their respective open contacts in response to a maximum level of the environmental condition at the given time, and is further configured to integrate the digital outputs over time using the clock speed of the clock without use of an arithmetic logic unit.

32. The method according to claim 25, wherein at least one clock generates multiple different clock speeds that are assigned to the digital outputs of the sensing elements to generate the system output.

33. The method according to claim 32, further comprising assigning higher clock speeds to the digital outputs of the sensing elements responsive to higher levels of the environmental condition.

34. The method according to claim 25, wherein the digital outputs of only a subset of the sensing elements are processed by the integrated circuitry to generate the system output of the sensing system, and a remainder of the sensing elements is ignored by the integrated circuitry when generating the system output.

35. The method according to claim 34, wherein the remainder of the sensing elements are responsive to levels of the environmental condition outside a range defined by the levels of the environmental condition to which the subset of sensing elements are responsive.

36. The method according to claim 25, wherein a first set of the sensing elements are responsive to temperature and a second set of the sensing elements are responsive to relative humidity.

37. The method according to claim 25, further comprising temperature compensating each of the second set of the sensing elements with a temperature switch electrically connected therewith.

38. The method according to claim 37, wherein the temperature switches are electrically connected to the second set of sensing elements in series and in shunt configurations.

39. The method according to claim 37, wherein the second set of sensing elements comprises subsets of the sensing elements connected in parallel, each subset defines a humidity switch, and each of the sensing elements within each humidity switch is electrically connected to a corresponding one of the temperature switches.

40. The method according to claim 39, wherein the sensing elements within each humidity switch contact and close their respective open contacts at different levels of relative humidity.

41. The method according to claim 40, wherein the sensing elements and the temperature switches within each humidity switch cooperate to yield a single digital signal over a limited temperature range determined by the temperature switches.

42. The method according to claim 41, wherein the temperature switches are electrically connected to their respective sensing elements in series and in shunt configurations.

43. The method according to claim 25, further comprising wirelessly transmitting the system output via a radio frequency identification link.

44. The method according to claim 25, wherein the integrated circuitry generates the system output as a digital system output directly from the digital outputs of the sensing elements without performing any analog-to-digital conversion of the digital outputs of the sensing elements.

45. The method according to claim 25, further comprising the steps of:

testing the sensing elements to correlate the digital outputs thereof to the environmental condition;

identifying a subset of the sensing elements that produce digital outputs corresponding to a predetermined range of levels of the environmental condition; and

then

causing the integrated circuitry to interface with only the subset of the sensing elements so that the system output is generated using the digital outputs of only the subset of the sensing elements while a remainder of the sensing elements is ignored by the integrated circuitry when generating the system output.

46. A method of producing a micro-electro-mechanical digital sensing system, the method comprising the steps of:

fabricating a sensing system comprising integrated circuitry and a plurality of contact-mode sensing elements, the sensing elements being responsive to an environmental condition and operable to close at least one pair of open contacts at different levels of the environmental condition to individually produce digital outputs;

determining responses of the sensing elements to different levels of the environmental condition;

selecting a subset of the sensing elements that produce digital outputs corresponding to a predetermined range of levels of the environmental condition; and

then

configuring the integrated circuitry to process the digital outputs of only the subset of the sensing elements with the integrated circuitry to generate a system output of the sensing system while a remainder of the sensing elements is ignored by the integrated circuitry when generating the system output.

47. The method according to claim 46, wherein the environmental condition to which the sensing elements are responsive is at least one environmental condition chosen from the group consisting of temperature, relative humidity, chemicals, shock/vibration, tilt, pressure, acceleration, and biological agents.

48. The method according to claim 46, wherein at least some of the sensing elements are fabricated to be responsive to temperature and at least some of the sensing elements are fabricated to be responsive to relative humidity.

49. The method according to claim 46, wherein the integrated circuitry generates the system output as a time-weighted cumulative output generated on the basis of the digital outputs of the subset of the sensing elements over time.

50. The method according to claim 46, wherein the remainder of the sensing elements are responsive to levels of the environmental condition outside a range defined by the levels of the environmental condition to which the subset of sensing elements are responsive.

51. The method according to claim 46, wherein the sensing system is produced without individually calibrating the sensing elements.

52. The method according to claim 46, wherein the sensing system is produced without physically modifying and without electronically compensating any of the sensing elements to alter the responses of the sensing elements to the environmental condition after the selecting step.