Measuring of fluid in a vessel with two coaxial cable sections and a coupling therebetween using time domain reflectometry

1. An apparatus for measuring a level of a liquid comprising:

a first coaxial cable section including a first center conductor, a first outer conductor and a solid dielectric between the first center conductor and first outer conductor;

a second coaxial cable section including a second center conductor wherein the second center conductor is a unitary extension of the first center conductor, a second outer conductor and an air dielectric between the second center conductor and second outer conductor; and

a coupling between the first and second coaxial cable sections, wherein the second coaxial cable section is disposed in a liquid for determining a level of the liquid;

wherein the coupling includes a center conductor, an outer conductor and a dielectric extending therebetween, and at least part of the dielectric of the coupling is an air dielectric and communicates with the air dielectric of the second coaxial cable section.

2. The apparatus as in claim 1 , wherein the second coaxial cable section includes an end cap.

3. The apparatus as in claim 2 , wherein the end cap includes at least one vent aperture to permit fluid or air to flow therethrough.

4. The apparatus as in claim 1 , wherein the outer conductor of the coupling includes at least one vent aperture to provide communication between the air dielectrics of the coupling and the second coaxial cable section to the ambient surroundings.

5. The apparatus as in claim 4 , wherein the coupling is configured to permit the first and second coaxial cable sections to be aligned at a predetermined angle to one another.

6. A fluid level gauge assembly for measuring a level of a fluid in a fluid container, the fluid container including a top, a bottom and at least one side wall, the fluid level gauge assembly comprising:

a first coaxial cable section having a first end and a second end, the first coaxial cable section including a first center conductor, a first outer conductor and a solid dielectric between the first center conductor and first outer conductor;

a second coaxial cable section having a first end and a second end, the second coaxial cable section including a second center conductor wherein the second center conductor is a unitary extension of the first center conductor, a second outer conductor and an air dielectric between the second center conductor and second outer conductor; and

a coupling between the second end of the first coaxial cable section and the first end of the second coaxial cable section, wherein the second coaxial cable section is disposed in a fluid for determining a level of the fluid, the coupling includes a center conductor, an outer conductor and a dielectric extending therebetween, and at least part of the dielectric of the coupling is an air dielectric and communicates with the air dielectric of the second coaxial cable section.

7. The fluid level gauge assembly as in claim 6 , wherein the first end of the first coaxial cable section is configured for connection to a time domain reflectometer.

8. The fluid gauge assembly as in claim 6 , wherein the coupling is coupled to the top of the fluid container and the second end of the second coaxial cable section is disposed adjacent to the bottom of the fluid container.

9. The fluid gauge assembly as in claim 8 , wherein the coupling is configured to permit the first and second coaxial cable sections to be aligned at a predetermined angle to one another.

10. The fluid gauge assembly as in claim 8 , wherein the second end of the second coaxial cable section is positioned a predetermined distance from the bottom of the fluid container.

11. The fluid gauge assembly as in claim 10 , further comprises an end cap disposed on the second end of the second coaxial cable section.

12. The fluid gauge assembly as in claim 11 , wherein the end cap includes at least one vent aperture to permit fluid or air to flow therethrough.

13. The fluid gauge assembly as in claim 6 , wherein the coupling is coupled to the bottom of the fluid container and the second end of the second coaxial cable section is disposed adjacent to the top of the fluid container.

14. The fluid gauge assembly as in claim 6 , wherein the outer conductor of the coupling includes at least one vent aperture to provide communication between the air dielectrics of the coupling and the second coaxial cable section to the ambient surroundings.