Radio frequency identification sensor for fluid level

• US 20050017727A1
• Filed: 05/05/2004
• Published: 01/27/2005
• Est. Priority Date: 05/06/2003
• Status: Active Grant

• Current Assignee: RCD Technology Corporation
• Original Assignee: RCD Technology Corporation
• Inventors: Oberle, Robert R.
• Granted Patent: US 7,456,752 B2
• Time in Patent Office: Days
• US Class Current: 324/450
• CPC Class Codes: G01N 27/023 where the material is placed in the field of a coil
• CPC Class Codes: G01N 27/221 by investigating the dielectric properties using microwaves G01N22/00; measuring loss factors or dielectric constants per se G01R27/26

Abstract

A sensor can detect the presence of fluid by the changing of the response characteristics of an RLC circuit. A window in the sensor is used to position a short caused by the fluid.

Claims

1. A fluid sensor comprising:

a substrate; and

a tuned RLC circuit configured on the substrate, the tuned RLC circuit including an inductor coil and a capacitor coupled through said substrate, and

a film configured to limit exposure of the inductor coil to fluid, the film having one or more windows positioned such that fluid exposure is defined by the one or more windows, wherein fluid introduced through the one or more windows can cause a short in the RLC circuit.

2. The fluid sensor of claim 1, wherein the presence of the fluid modifies the response characteristics of the RLC circuit such that the fluid sensor can be used in a three state system where the fluid sensor in the presence of fluid has a different response characteristic from an absent fluid sensor.

3. The fluid sensor of claim 1, wherein fluid in the one or more windows can produce an electrical short across two or more turns of the inductor coil.

4. A method using the fluid sensor of claim 1, comprising detecting exposure to a fluid by measuring the change in resonant frequency of the tuned RLC during exposure to an electrically conductive fluid though the window in the film.

5. A method using the fluid sensor of claim 1, comprising detecting exposure to a fluid by measuring the change in impedance of the RLC circuit before and after exposure to an electrically conductive fluid.

6. The fluid sensor of claim 1, wherein the fluid sensor is initially tuned to a frequency between 6 MHz and 25 MHz.

7. The fluid sensor of claim 1, wherein the window is positioned such that the fluid exposure causes a predictable change in resonant frequency of the circuit.

8. The fluid sensor of claim 1, wherein the window is positioned such that the fluid exposure causes a predictable change in electrical impedance of the circuit.

9. The fluid sensor of claim 1, wherein the window is outside of the area of the inductive coil.

10. The fluid sensor of claim 1, wherein an exposure to an electrically conductive fluid causes a shift in resonant frequency through a change in capacitance of the circuit.

11. The fluid sensor of claim 1, wherein an exposure to an electrically conductive fluid causes a shift in resonant frequency through a change in inductance of the circuit.

12. The fluid sensor of claim 1, wherein an exposure to an electrically conductive fluid causes a shift in resonant frequency through a change in resistance of the circuit.

13. The fluid sensor of claim 1, wherein the one or more windows in the is covered with a material that becomes conductive upon exposure to a fluid containing a specific component or class of components.

14. The fluid sensor of claim 13, wherein there are multiple windows at least two of are independently covered with differing receptive/reactive compounds that become conductive in response to exposure to differing components of the fluid.

15. The fluid sensor of claim 1, wherein the sensor is coupled to an active, dedicated monitoring unit which provides data to a control/host information network on demand.

16. The fluid sensor of claim 1, wherein the substrate is non-porous.

17. A sensor comprising:

a substrate; and

a tuned RLC circuit configured on the substrate, the tuned RLC circuit including an inductor coil and a capacitor coupled through said substrate, and

a film configured to limit exposure of the inductor coil to an environmental element, the film having one or more windows positioned such that environmental exposure is defined by the one or more windows, wherein an environmental element introduced through the one or more windows can cause a short in the RLC circuit.

18. The sensor of claim 17, wherein the environmental element is a fluid.

19. the sensor of claim 18 wherein the fluid is a conductive fluid.

20. The sensor of claim 18 wherein the environmental element reacts with material in the window to produce the short.

21. A fluid sensor comprising:

first and second tuned RLC circuits formed on at least one substrate, the first and second tuned RLC circuits including inductor coils and capacitors coupled through said at least one substrate, wherein the first and second tuned RLC circuits have different responses to the introduction of fluid, and wherein at least one of the first and second tuned RLC circuits changes its response characteristics with the introduction of a fluid at the fluid sensor.

22. The fluid sensor of claim 21, wherein the first RLC circuit is protected from fluid so that its response characteristics does not change with the introduction of a fluid at the fluid sensor.

23. The fluid sensor of claim 22, wherein the second RLC circuit has a film configured to limit exposure of the inductor coil to fluid, the film having one or more windows positioned such that fluid exposure is defined by the one or more windows, wherein fluid introduced through the one or more windows can cause a short in the RLC circuit.

24. The fluid sensor of claim 22, wherein the second RLC circuit is unprotected from fluid.

25. The fluid sensor of claim 21, wherein the first RLC circuit has a film configured to limit exposure of the inductor coil to fluid, the film having one or more windows positioned such that fluid exposure is defined by the one or more windows, wherein fluid introduced through the one or more windows can cause a short in the RLC circuit.

26. The fluid sensor of claim 25, wherein the second RLC circuit has a film configured to limit exposure of the inductor coil to fluid, the film having one or more windows positioned in a different arrangement from first RLC circuit, the fluid exposure is defined by the one or more windows.

27. The fluid sensor of claim 21, wherein the second RLC circuit is unprotected from fluid.

28. The fluid sensor of claim 21, further comprising additional RLC circuits.