CONTACTLESS RESISTANCE MEASUREMENT

• US 20150293158A1
• Filed: 04/11/2014
• Published: 10/15/2015
• Est. Priority Date: 04/11/2014
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Widener, Steven Rowland
• Granted Patent: US 9,625,506 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G01K 7/22 the element being a non-linear resistance, e.g. thermistor G01K7/26 takes precedence
• CPC Class Codes: G01R 27/02 Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant by measuring phase angle only G01R25/00

Abstract

A resistance is measured without physical contact/connection to the resistance. A resistive element to be measured is provided, physically connected as part of a passive electrical circuit. Without physically contacting the resistive element, an electromagnetic field is used to produce an excitation in the passive electrical circuit. The resistance of the resistive element is determined based on an effect of the excitation on the electromagnetic field.

Claims

1. A method for non-contact resistance measurement, comprising:

providing a resistive element that is physically connected as part of a passive electrical circuit; and

without physically contacting the resistive element,

using an electromagnetic field to produce an excitation in the passive electrical circuit, and

determining a resistance of the resistive element based on an effect of said excitation on said electromagnetic field.

2. The method of claim 1, wherein the passive electrical circuit includes an inductor connected in parallel with the resistive element.

3. The method of claim 2, wherein said using includes maintaining the passive electrical circuit in a predetermined positional relationship relative to a measurement device that produces said electromagnetic field, and wherein said determining includes using the measurement device, during said maintaining, to make a measurement that corresponds to said effect of said excitation on said electromagnetic field.

4. The method of claim 3, wherein said determining includes evaluating said measurement relative to a plurality of further said measurements, each said further measurement corresponding to a respective further passive electrical circuit, wherein each said further passive electrical circuit has a respective known resistance connected in parallel with a further inductor having an inductance equal to that of said inductor, and wherein each said further passive electrical circuit is maintained, during the corresponding further measurement, in said predetermined positional relationship with the measurement device.

5. The method of claim 4, wherein said determining includes making a resistance determination for the resistive element based on said evaluating.

6. The method of claim 5, including obtaining a calibration relationship for said plurality of further measurements in order to compensate for a difference between first operating conditions associated with said measurement and second operating conditions associated with said plurality of further measurements.

7. The method of claim 6, wherein said calibration relationship is based on another said measurement performed under said first operating conditions and corresponding to one of said further passive electrical circuits, wherein said one of said further passive electrical circuits is, during said another measurement, maintained in said predetermined positional relationship with the measurement device.

8. The method of claim 7, including applying said calibration relationship to the resistance determination in order to obtain a calibrated resistance determination for the resistive element.

9. The method of claim 8, including applying said calibration relationship to a plurality of said resistance determinations that respectively correspond to a plurality of said predetermined positional relationships to obtain a plurality of calibrated resistance determinations, and combining said calibrated resistance determinations to obtain a final resistance determination for the resistive element.

10. The method of claim 5, wherein said determining includes making a plurality of said resistance determinations that respectively correspond to a plurality of said predetermined positional relationships, and combining said resistance determinations to obtain a final resistance determination for the resistance element.

11. The method of claim 10, wherein said combining includes averaging said resistance determinations.

12. The method of claim 3, wherein said predetermined positional relationship includes a winding axis of said inductor coaxially aligned with a winding axis of an inductor in the measurement device.

13. The method of claim 12, wherein said predetermined positional relationship includes said measurement device and said passive electrical circuit spaced apart from one another by a predetermined distance.

14. The method of claim 3, wherein said measurement indicates a distance between the passive electrical circuit and the measurement device.

15. The method of claim 3, wherein the measurement device is an LDC1000 inductance-to-digital converter.

16. The method of claim 1, wherein said passive electrical circuit is provided in a thermistor.

17. The method of claim 16, including repeating said using and said determining for a plurality of different temperatures of the thermistor.

18. The method of claim 1, wherein said resistive element includes a blood/reagent mixture.

19. The method of claim 1, wherein said resistive element is provided in a manufactured product and the resistance of said resistive element is associated with an item of information about the manufactured product.

20. The method of claim 1, wherein said passive electrical circuit includes an inductor and a capacitor each connected in parallel with the resistive element.