Isolated gas sensor configuration

1. A gas sensor assembly for detecting a constituent in a gaseous stream, the assembly comprising:

(a) a mounting surface having a central portion formed on a flexible circuit such that said central portion of said mounting surface does not contact underlying components of said sensor assembly;

(b) a sensor mounted on the mounting surface, said sensor capable of generating a detectable signal in the presence of said constituent; and

(c) an enclosing structure comprising:

(i) a walled component having a pair of vertically spaced ends, the walled component mounted at one end on said mounting surface and circumscribing said sensor; and

(ii) a gas-permeable membrane attached at the other end of said walled component, thereby defining an interior volume within said enclosing structure, said gas-permeable membrane having optical properties that inhibit passage of light into said interior volume;

whereby flowing the gaseous stream across said gas-permeable membrane infuses a portion of the gaseous stream into said interior volume containing said sensor.

2. The gas sensor assembly of claim 1 wherein said gas-permeable membrane is non-transparent.

3. The gas sensor assembly of claim 2 wherein said gas-permeable membrane is opaque.

4. The gas sensor assembly of claim 1 wherein said gas-permeable membrane is polymeric.

5. The gas sensor assembly of claim 1 wherein the gas-permeable membrane is a polytetrafluoroethylene-based membrane material.

6. The gas sensor assembly of claim 1 wherein said sensor is sensitive to hydrogen.

7. The gas sensor assembly of claim 6 wherein said sensor is catalytically activated.

8. The gas sensor assembly of claim 1 wherein said walled component is tubular.

9. The gas sensor assembly of claim 1 wherein said walled component is formed from an electrically insulative material.

10. The gas sensor assembly of claim 9 wherein the electrically insulative material is polymeric.

11. The gas sensor assembly of claim 10 wherein the electrically insulative material is an acetal resin.

12. A method of isolating, in a gas sensor assembly, a sensor capable of generating a detectable signal in the presence of a gas stream constituent, the method comprising:

(a) mounting said sensor on a mounting surface having a central portion formed on a flexible circuit such that said central portion of said mounting surface does not contact underlying components of said sensor assembly; and

(b) enclosing said sensor in an enclosing structure comprising:

(i) a walled component having a pair of vertically spaced ends, the walled component mounted at one end on said mounting surface and circumscribing said sensor; and

(ii) a gas-permeable membrane attached at the other end of said walled component, thereby defining an interior volume within said enclosing structure, said gas-permeable membrane having optical properties that inhibit passage of light into said interior volume;

whereby flowing the gaseous stream across said gas-permeable membrane infuses a portion of the gaseous stream into said interior volume containing said sensor.

13. The method of claim 12 wherein said gas-permeable membrane is non-transparent.

14. A method of detecting a constituent in a gaseous stream, the method comprising:

(a) mounting a sensor on a mounting surface having a central portion, said sensor capable of generating a detectable signal in the presence of said constituent;

(b) enclosing said sensor in an enclosing structure comprising:

(i) a walled component having a pair of vertically spaced ends, the walled component mounted at one end on said mounting surface such that said central portion of said mounting surface does not contact underlying components of said sensor assembly; and

(ii) a gas-permeable membrane attached at the other end of said walled component, thereby defining an interior volume within said enclosing structure, wherein said gas-permeable membrane has optical properties that inhibit the passage of light into said interior volume;

(d) flowing the gaseous stream across said gas-permeable membrane whereby a portion of said gaseous stream infuses into said interior volume and the impinges upon said sensor; and

(e) generating a detectable signal from said sensor in the presence of said constituent.

15. The method of claim 14 wherein said gas-permeable membrane is non-transparent.