Humidity sensor and method for monitoring moisture in concrete

• US 20070058898A1
• Filed: 06/30/2006
• Published: 03/15/2007
• Est. Priority Date: 06/30/2005
• Status: Abandoned Application

• Current Assignee: Infoscitex
• Original Assignee: Infoscitex
• Inventors: Slade, Jeremiah, Lusignea, Richard, Everson, Jeffrey, Kokkins, Stephan, Kristoff, Susan
• Application Number:
  US11/479,984
• Publication Number:
  US 20070058898A1
• Time in Patent Office: Days
• US Class Current: 385/12
• CPC Class Codes: G01N 2021/7723 Swelling part, also for adsorption sensor, i.e. without chemical reaction
• CPC Class Codes: G01N 21/774 the reagent being on a grating or periodic structure
• CPC Class Codes: G01N 21/81 Indicating humidity
• CPC Class Codes: G01N 33/383 Concrete or cement
• CPC Class Codes: G02B 6/022 using mechanical stress, e.g. tuning by compression or elongation, special geometrical shapes such as "dog-bone" or taper G02B6/02204 takes precedence; optical modulation using photo-elastic effect G02F1/0131
• CPC Class Codes: G02B 6/02204 using thermal effects, e.g. heating or cooling of a temperature sensitive mounting body optical modulation using thermo-optic effect G02F1/0147

Abstract

A humidity sensor and method is disclosed. The sensor is configured as an optical fiber based sensor and may be useful in obtaining moisture information, such as humidity and/or relative humidity (RH) in curing concrete. The sensor may be configured to isolate the sensor from external mechanical stresses, chemical reactions and/or temperature fluctuations that may occur in the concrete and/or at least account for such occurrences. Methods of calibrating the sensor are also disclosed. The sensor may be configured as a fiber Bragg sensor.

Claims

1. A kit of parts, comprising:

an openable, non-porous package defining a chamber, wherein the chamber is held at a relatively high humidity; and

,

a fiber optic based humidity sensor enclosed within the package.

2. The kit of claim 1, wherein the fiber optic based sensor comprises a fiber Bragg grating sensor.

3. The kit of claim 2, wherein the fiber Bragg grating sensor comprises an optical fiber with a hygroscopic coating thereon.

4. The kit of claim 3, wherein the hygroscopic coating comprises polyimide.

5. The kit of claim 3, wherein the fiber Bragg grating sensor comprises a selectively permeable covering adapted to substantially allow water vapor to flow through the covering and substantially prevent liquid water to flow through the covering.

6. The kit of claim 5, wherein the covering comprises PTFE.

7. The kit of claim 3, wherein the fiber Bragg grating sensor comprises a relatively rugged container, the container positioned over the optical fiber with the hygroscopic coating thereon and the covering.

8. The kit of claim 7, wherein the container is porous.

9. The kit of claim 7, wherein the container is a metal sleeve.

10. The kit of claim 1, further comprising a temperature sensor enclosed within the package.

11. The kit of claim 10, wherein the temperature sensor is a fiber Bragg grating sensor comprising an optical fiber with a hygroscopic coating thereon.

12. The kit of claim 11, wherein the hygroscopic coating comprises acrylate.

13. The kit of claim 1, further comprising a temperature sensor enclosed within the package, wherein the humidity sensor and the temperature sensor each comprise an optical fiber with a hygroscopic coating thereon, wherein the humidity sensor and the temperature sensor are disposed on a single optical fiber.

14. The kit of claim 1, further comprising a moisture element disposed within the package, the moisture element configured to provide moisture in the chamber.

15. The kit of claim 14, wherein the moisture element comprises a sponge.

16. A method of calibrating a fiber optic based humidity sensor, the method comprising:

a) placing the sensor in a humidity chamber that is at a relatively high humidity, without first placing the sensor in the humidity chamber at a relatively low humidity;

b) thereafter reducing the humidity within the chamber;

c) obtaining a signal from the sensor; and

d) correlating the obtained signal with the humidity in the chamber.

17. The method of claim 16, further comprising repeatedly performing b), c) and d), in order, until a desired range of signals are obtained.

18. The method of claim 17, wherein placing the sensor in a humidity chamber that is at a relatively high humidity comprises placing the sensor in a humidity chamber that is at approximately 95% relative humidity.

19. The method of claim 18, wherein reducing the humidity within the chamber comprises reducing the humidity within the chamber by approximately 5% increments.

20. The method of claim 18, wherein reducing the humidity within the chamber comprises reducing the humidity within the chamber by approximately 1% increments.

21. The method of claim 16, wherein placing the sensor in a humidity chamber that is at a relatively high humidity comprises placing the sensor in a humidity chamber that is at approximately 100% relative humidity.

22. The method of claim 21, wherein reducing the humidity within the chamber comprises reducing the humidity within the chamber by approximately 5% increments.

23. The method of claim 21, wherein reducing the humidity within the chamber comprises reducing the humidity within the chamber by approximately 1% increments.