Method and apparatus for determining average environmental conditions

• US 6,927,687 B2
• Filed: 07/09/2002
• Issued: 08/09/2005
• Est. Priority Date: 07/09/2002
• Status: Active Grant

• Current Assignee: Battelle Memorial Institute
• Original Assignee: Battelle Memorial Institute
• Inventors: Carrender, Curt
• Primary Examiner(s): GOINS, DAVETTA WOODS
• Application Number:
  US10/192,287
• Publication Number:
  US 20040008112A1
• Time in Patent Office: 1,127 Days
• Field of Search: 340/539.26, 340/572.1, 340/505, 340/502, 340/501, 340/622, 340/10.1, 340/10.4, 340/540, 340/539.1, 340/539.22, 340/539.27, 340/825.54
• US Class Current: 340/539.26
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor
• CPC Class Codes: G06K 19/0717 the sensor being capable of sensing environmental conditions such as temperature history or pressure

Abstract

A system for monitoring an environmental condition and determining the average environmental condition using an RFID tag and reader, the tag configured to have at least one module with known characteristics that are dependent on the environmental condition and to be responsive to interrogation by the reader to asses the state of the known characteristics for determining the average environmental condition.

Claims

1. A device for measuring environmental conditions, comprising:

a first module having known characteristics dependent on at least one environmental condition;

a second module having known characteristics dependent on the at least one environmental condition and that are different than the known characteristics of the first module;

the first and second modules configured to be responsive to radio frequency interrogation of a state of their respective known characteristics for assessing an average of the at least one environmental condition.

2. The device of claim 1 wherein the at least one environmental condition comprises temperature.

3. A method for detecting an environmental condition during an unpowered state of an RFID tag, the method comprising:

providing an RFID tag having a first device with known characteristics dependent on the environmental condition and a second device with known characteristics dependent on the environmental condition and that are different than the known characteristics of the first device;

interrogating the RFID tag to assess a state of the known characteristics of the first and second devices; and

determining an average of the environmental condition in response to the state of the known characteristics of the first and second devices.

4. The method of claim 3 wherein the environmental condition comprises temperature.

5. A system for determining an average of at least one environmental condition, comprising:

a device for measuring the at least one environmental condition, the device comprising a first module having known characteristics dependent on the at least one environmental condition and a second module having known characteristics dependent on the at least one environmental condition and that are different than the characteristics of the first module, the device configured to respond to a radio frequency interrogation of a state of the known characteristics of the first and second modules; and

a device for interrogating the measuring device to assess the state of the known characteristics for determining an average of the at least one environmental condition in response thereto.

6. The system of claim 5 wherein the at least one environmental condition comprises temperature.

7. A method of monitoring temperature during an unpowered state of a radio frequency device, the method comprising:

providing a radio frequency device comprising a first assembly having known characteristics that are dependent on temperature and a second assembly having known characteristics that are dependent on temperature and that are different than the known characteristics of the first assembly;

exposing the radio frequency device to the temperature;

interrogating the radio frequency device to determine a state of the first and second assemblies; and

calculating average temperature of the radio frequency device utilizing the state and the known characteristics of the first and second assemblies.

8. The method of claim 7, further comprising determining elapsed time of exposure of the radio frequency device.

9. The method of claim 7 wherein the known characteristics comprise the rate of dissipation of a stored charge and the state comprises the amount of the stored charge.

10. The method of claim 9 wherein the charge is stored in a leaking junction of an integrated device.

11. The device of claim 9 wherein the charge is stored in a super capacitor that discharges at a rate dependent on temperature.

12. The method of claim 9 wherein the charge is stored in a thin-oxide EEPROM having a rate of charge leakage dependent on temperature.

13. The method of claim 9 wherein the charge is stored on a persistent node having a charge leakage dependent on temperature.

14. The method of claim 9 wherein the charge is stored in an electro-chemical device that discharges at a rate dependent on temperature.

15. The method of claim 7 wherein the known characteristics comprise an oscillator having an oscillation frequency that varies in response to changes in temperature.

16. The method of claim 7 wherein the known characteristics comprise a variable resistance that changes in response to changes in the temperature.

17. The method of claim 7 wherein the known characteristics comprise magnetic flux that varies in response to changes in temperature.

18. The method of claim 7 wherein the RF device is time-stamped by a reader to determine exposure time of the RF device.

19. A method of monitoring average temperature during an unpowered state of a radio frequency (RF) device, the method comprising:

providing a RF device having at least two sensors with known characteristics that respond to changes in temperature at different rates of change;

exposing the RF device to the temperature;

powering the RF device and calibrating the RF device for improving accuracy;

interrogating the RF device to determine the states of the sensors; and

calculating average temperature using the determined states of the sensors.

20. A method of monitoring an average environmental condition during an unpowered state of an RF device, comprising:

providing an RF device comprising a first sensor having a first sensitivity to the environmental condition, and a second sensor having a second sensitivity to the environmental condition that is different than the first sensitivity of the first sensor;

exposing the RF device to the environmental condition;

interrogating the RF device to determine a state of each of the first and second sensors; and

calculating elapsed time and change in state of the first and second sensors to determine an average environmental condition.

21. The method of claim 20 wherein the known characteristics comprise rate of dissipation of a stored charge.

22. A device for monitoring temperature, comprising:

a first monitoring device configured to change electrical charge state over time and at a first rate in response to variations in its temperature;

a second monitoring device configured to change electrical charge state over time at a second rate in response to variations in its temperature; and

an RFID circuit coupled to the first and second monitoring devices and configured to transmit the state of the electrical charge in the first and second monitoring devices in response to an interrogation signal.

23. The device of claim 22 wherein the rate of change of electrical charge state of at least one of the first and second monitoring devices is non-linear.