COAXIAL CABLE BRAGG GRATING SENSOR

• US 20120272741A1
• Filed: 04/02/2012
• Published: 11/01/2012
• Est. Priority Date: 04/01/2011
• Status: Active Grant

• Current Assignee: Habsonic LLC
• Original Assignee: Habsonic LLC
• Inventors: Xiao, Hai, Fan, Jun, Wei, Tao, Wu, Songping
• Granted Patent: US 9,046,342 B2
• Time in Patent Office: Days
• US Class Current: 73/774
• CPC Class Codes: G01B 15/06 for measuring the deformation in a solid
• CPC Class Codes: G01B 7/16 for measuring the deformation in a solid, e.g. by resistance strain gauge
• CPC Class Codes: G01L 1/246 using integrated gratings, e.g. Bragg gratings
• CPC Class Codes: G01L 5/04 for measuring tension in flexible members, e.g. ropes, cables, wires, threads, belts or bands G01L5/0004 takes precedence
• CPC Class Codes: Y10T 29/53022 with means to test work or product

Abstract

A coaxial cable sensor device with periodic impedance discontinuities along the length of its cable. The cable comprises an inner conductor, insulating material disposed around the length of the inner conductor, and an outer conductor disposed around the insulating material. The periodic impedance discontinuities are created by physical deformations or material alterations to at least one of the inner conductor, the outer conductor, and the insulating material. The sensor device may be used to measure temperature, pressure, strain, and acoustic waves in building structures, and is well suited for down-hole or underwater applications.

Claims

1. A coaxial cable sensing device for detecting and measuring strain applied thereto comprising:

an inner conductor extending a length of the coaxial cable sensing device;

an outer conductor extending the length of the coaxial cable sensing device; and

an insulating material disposed between the inner conductor and the outer conductor, said insulating material electrically insulating the outer conductor from the inner conductor;

wherein at least one of the inner conductor, the insulating material, and the outer conductor includes one or more impedance discontinuities along its respective length.

2. The coaxial cable sensing device of claim 1, wherein the insulating material is a dielectric material.

3. The coaxial cable sensing device of claim 1, wherein the impedance discontinuities are physical deformations periodically spaced along the length of the at least one of the inner conductor, the insulating material, and the outer conductor.

4. The coaxial cable sensing device of claim 3, wherein the physical deformations comprise dimensional changes.

5. The coaxial cable sensing device of claim 4, wherein the dimensional changes are created by one or more deformed metal sleeves disposed around the coaxial cable sensing device along the length of the coaxial cable sensing device.

6. The coaxial cable sensing device of claim 1, wherein the impedance discontinuties comprise material alterations of the at least one of the inner conductor, insulating material, and the outer conductor.

7. The coaxial cable sensing device of claim 6, wherein the material alterations comprise periodic holes in the at least one of the inner conductor, the insulating material, and the outer conductor.

8. The coaxial cable sensing device of claim 7, wherein one or more lasers form the holes in the at least one of the inner conductor, the insulating material, and the outer conductor.

9. The coaxial cable sensing device of claim 1, further comprising at least one connector attached at an end of the cable, said connector permitting one or more external devices to transmit a signal into at least one of the inner conductor and the conductor and to measure the transmission and reflection properties of the coaxial cable sensing device as a function of the transmitted signal.

10. A method for detecting environmental properties of a target environment using a coaxial cable sensing device, said method comprising:

identifying one or more environmental properties of the target enviroment for detection;

determining a calibration curve for the coaxial cable sensing device with respect to the target environment for each identified environmental property;

positioning the coaxial cable sensing device in the target environment, said coaxial cable sensing device having periodic impedance discontinuities along its length;

interrogating the coaxial cable sensing device to detect frequency changes of the coaxial cable sensing device;

measuring said frequency changes of the coaxial cable sensing device; and

analyzing the measured frequency changes against the each calibration curve.

11. The method of claim 10, wherein the calibration curve for each identified environmental property includes baseline information for the coaxial cable with respect to the identified environmental property.

12. The method of claim 10, wherein analyzing the measured frequency changes comprises identifying deviations between the measured frequency changes, said deviations indicative of a change in the identified environmental property

13. The method of claim 12, wherein the analyzed frequency changes indicate a change in at least one of a temperature, a pressure, a strain, or acoustic waves in the target enviroment.

14. An automated system for manufacturing a coaxial cable sensor having a plurality of impedance discontinuities periodically spaced along its length, with each adjacent discontinuity having the same predefined period distance between it and the next adjacent discontinuity, said coaxial cable sensor having an inner conductor, an insulating material disposed around the inner conductor, and an outer conductor disposed around the insulating material, said system comprising:

a coaxial cable positioned on a platform by at least a first cable guide and a second cable guide, said coaxial cable introduced into the automated system by the first cable guide;

a coaxial cable spooler for pulling the coaxial cable through the first cable guide and the second cable guide;

a discontinuity creation device for creating periodic impedance discontinuities in the coaxial cable as the coaxial is pulled through the first cable guide and the second cable guide, said discontinuity creation device positioned between the first cable guide and the second cable guide;

an imaging device for acquiring an image of each created discontinuity, said imaging device positioned between the discontinuity creation device and the second cable guide, said imaging device positioned at a predetermined distance from the discontinuity creation device; and

a computing device for determining the distance between two adjacent discontinuities created by the discontinuity creation device and synchronizing the rate of spin of the cable spooler based on the determined distance between the two adjacent discontinuities and determined distance between the imaging device and the discontinuity creation device to move the coaxial cable a distance equal to the predefined period distance within an acceptable tolerance.

15. The system of claim 14, wherein the first and second cable guides comprise double-sides, spring-driven clamps exerting a substantially constant force on the cable.

16. The system of claim 14, wherein the discontinuity created by the discontinuity creation device is a physical deformation to at least one of the inner conductor, the insulating material, and the outer conductor of the coaxial cable at a point on the coaxial cable as it is pulled through the first cable guide and the second cable guide by the cable spooler controlled by the computing device.

17. The system of claim 16, wherein the discontinuity creation device creates the physical deformation by placing a deformed metal sleeve around the coaxial cable at a point on the coaxial cable, said deformed metal sleeve causing a dimensional change to the coaxial cable.

18. The system of claim 14, the discontinuity created by the discontinuity creation device is a material alteration of the at least one of the inner conductor, insulating material, and the outer conductor at a point on the coaxial cable as it is pulled through the first cable guide and the second cable guide by the cable spooler controlled by the computing device.

19. The system of claim 18, wherein the material alterations comprise one or more holes in the at least one of the inner conductor, the insulating material, and the outer conductor.

20. The system of claim 19, wherein the discontinuity creation device includes a laser for forming the holes in the at least one of the inner conductor, the insulating material, and the outer conductor.