Methods and systems for calibration of RFID sensors

• US 7,911,345 B2
• Filed: 05/12/2008
• Issued: 03/22/2011
• Est. Priority Date: 05/12/2008
• Status: Active Grant

• Current Assignee: Westinghouse Air Brake Technologies Corporation
• Original Assignee: General Electric Company
• Inventors: Morris, William Guy, Potyrailo, Radislav Alexandrovich
• Primary Examiner(s): Hunnings; Travis R
• Application Number:
  US12/118,950
• Publication Number:
  US 20090278685A1
• Time in Patent Office: 1,044 Days
• Field of Search: 340/572.1, 340/10.1, 340/10.5
• US Class Current: 340/572.1
• CPC Class Codes: G01N 27/126 comprising organic polymers
• CPC Class Codes: G01N 33/0006 Calibrating gas analysers
• CPC Class Codes: G01N 33/0073 Control unit therefor
• 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 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 7/0095 Testing the sensing arrangement, e.g. testing if a magnetic card reader, bar code reader, RFID interrogator or smart card reader functions properly testing of electrical circuits G01R31/28

Abstract

Methods and systems for calibration of RFID sensors used in manufacturing and monitoring systems are provided. The methods include measuring impedance of an RFID sensor antenna, relating the measurement of impedance to one or more parameters (such as physical, chemical and biological properties), computing one or more analytical fit coefficients, and storing the one or more analytical fit coefficients on a memory chip of the RFID sensor. Measuring impedance of the RFID sensor may comprise measuring complex impedance which involves measuring complex impedance spectrum, phase angle and magnitude of the impedance, at least one of frequency of the maximum of the real part of the complex impedance, magnitude of the real part of the complex impedance, zero-reactance frequency, resonant frequency of the imaginary part of the complex impedance, and antiresonant frequency of the imaginary part of the complex impedance. Also provided are manufacturing or monitoring systems comprised of an RFID sensor wherein the RFID sensor comprises, a memory chip, an antenna, and a sensing film wherein analytical fit coefficients are stored on the memory chip to allow calibration of the RFID sensor. Also provided are manufacturing or monitoring systems comprised of an RFID sensor wherein the RFID sensor comprises, a memory chip, an antenna, and a complementary sensor attached to the antenna where the complementary sensor in a pre-calibrated fashion predictably affects the impedance of the antenna.

Claims

1. A method for calibration of an RFID sensor used in manufacturing and monitoring systems comprising:

measuring complex impedance of an RFID sensor antenna;

relating the measurement of impedance of the RFID sensor antenna to one or more parameters;

computing one or more analytical fit coefficients;

storing the one or more analytical fit coefficients on a memory chip of the RFID sensor; and

wherein measuring complex impedance comprises measuring at least one of frequency of magnitude of the real part of the complex impedance, resonance peak position of the real part of the complex impedance, resonant frequency of the imaginary part of the complex impedance, antiresonant frequency of the imaginary part of the complex impedance, zero-reactance frequency, quality factor of resonance, peak width, and peak symmetry of the complex impedance response of the antenna.

2. The method of claim 1 wherein measuring complex impedance comprises measuring phase angle and magnitude of the impedance.

3. The method of claim 1 wherein the one or more parameters are measurable variables within a manufacturing or monitoring system.

4. The method of claim 3 wherein the measurable variables comprises at least one of physical, chemical and biological properties.

5. The method of claim 4 wherein physical, chemical and biological properties comprises temperature, pressure, material concentration, conductivity, dielectric property, dose of ionizing radiation, and light intensity.

6. The method of claim 1 wherein the relating step comprises identifying a change in the measurement of complex impedance which correlates to a change in the one or more parameters.

7. The method of claim 6 wherein the change in one or more parameters relates to dimension, quantity or capacity of the one or more parameters.

8. The method of claim 6 wherein the relating step further comprises:

identifying a change in the measurement of complex impedance which correlates to a change in one or more interference factors; and

identifying a response relationship between the measurement of complex impedance and changes in the one or more parameters which occur in the presence of the one or more interference factors.

9. The method of claim 8 wherein the interference factors hinders, obstructs or impedes the relating the measurement of complex impedance of the RFID sensor antenna to the one or more parameters.

10. The method of claim 1 wherein the computing step comprises a univariate or a multivariate analysis.

11. The method of claim 1 wherein where the memory chip operates over at least one of the assigned radio frequency regions in the range from about 100 kHz to about 10 GHz.

12. The method of operating an RFID sensor calibrated according to claim 1 further comprising:

measuring complex impedance of an RFID sensor during exposure to one or more parameters;

converting the complex impedance into measurement values of the one or more parameters using the stored one or more analytical fit coefficients; and

optionally sending the measurement values of the one or more parameters to a display device or a control device.

13. The method of claim 12 further comprising:

obtaining measurement values of the one or more parameters using a reference measurement system;

comparing the measurement values of the one or more parameters using the reference measurement system to the measurement values from converting the complex impedance using the stored one or more analytical fit coefficients;

adjusting the analytical fit coefficients based on the compared measurement values; and

storing the adjusted analytical fit coefficients on the memory chip of the RFID sensor.

14. The method of claim 13 wherein the reference measurement system comprises measuring one or more parameters using a known standard.

15. The method of claim 14 wherein the known standard comprises at least one of a control sample, a manufactured calibrator, or a calibration-set.

16. The method of claim 1 wherein the measuring complex impedance of an RFID sensor occurs during a manufacturing or a monitoring process.

17. The method of claim 1 further comprising storing digital identification on the memory chip of the RFID sensor and optionally sending the stored data to a display device or a control device.

18. The method of claim 17 wherein the digital identification comprises at least one of information regarding part identification, assembly, use, correction coefficients, calibration, production history, shelf life, and expiration date for a component associated with the RFID sensor.

19. The method of claim 1 wherein the measurement of complex impedance of an RFID sensor antenna further comprising the measurement of complex impedance of a plurality of RFID sensor antennas.

20. The method of claim 1 wherein the RFID sensor further comprises a complementary sensor.

21. The method of operating an RFID sensor calibrated according to claim 1 further comprising:

measuring complex impedance of an RFID sensor during exposure to one or more parameters;

converting the complex impedance into measurement values of the one or more parameters using the stored one or more analytical fit coefficients;

storing measurement values in memory of the memory chip of the RFID sensor by writing the measurement values using a reader/writer device; and

optionally sending the measurement values of the one or more parameters to a display device or a control device.

22. A manufacturing or monitoring system comprising an RFID sensor wherein the RFID sensor comprises:

a memory chip;

an antenna;

a complementary sensor; and

wherein the complementary sensor is configured to provide a measured response to a change in a parameter and the measured response is selected from the group consisting of a change in the resistance of the complementary sensor, a change in capacitance of the complementary sensor, a change in inductance of the complementary sensor and combinations thereof.

23. The RFID sensor of claim 22 wherein the change in a parameter is chemical, physical or biological property.

24. The RFID sensor of claim 22 wherein the complementary sensor is connected to the antenna, the memory chip, or to both the antenna and the memory chip of the RFID sensor.

25. The RFID sensor of claim 22 further comprising digital identification stored on the memory chip of the RFID sensor.

26. The RFID sensor of claim 25 wherein the digital identification comprises at least one of information regarding part identification, assembly, use, correction coefficient, calibration, production history, shelf life, and expiration date for the component associated with the RFID sensor.

27. The RFID sensor of claim 22 wherein the RFID sensor is incorporated into a manufacturing device or a monitoring device.

28. The RFID sensor of claim 27 wherein the manufacturing device or the monitoring device comprises a plurality of RFID sensors.

29. The RFID sensor of claim 22 wherein the RFID sensor is part of a network device such as a computer laptop, cell phone, or personal digital assistant (PDA) and wherein the network device has an RFID reader to read at least one RFID sensor.