Gas sensors

• US 6,558,519 B1
• Filed: 07/27/1999
• Issued: 05/06/2003
• Est. Priority Date: 12/07/1996
• Status: Expired due to Term

• Current Assignee: Invensys Controls UK, Ltd. (Schneider Electric SE)
• Original Assignee: Central Research Fund Limited
• Inventors: Robins, Ian, Dodgson, John Robert, Austen, Malcolm Trayton
• Primary Examiner(s): Tung, T.
• Application Number:
  US09/319,446
• Time in Patent Office: 1,379 Days
• Field of Search: 204/401, 204/415, 204/412
• US Class Current: 204/401
• CPC Class Codes: G01N 33/007 Arrangements to check the analyser calibrating gas analysers G01N33/0006

Abstract

A gas sensor including a housing containing at least a sensing electrode, a counter electrode, a test electrode, and electrolyte means in contact with such electrodes. The housing permits gas from the environment to flow to the sensing electrode. The gas sensor is operable either in a normal mode of operation in which potentials are applied to the electrodes for detecting when a gas to be sensed is present at the sensing electrode, or in a test mode of operation in which potentials are applied to the electrodes so that the test electrode generates a gas which flows to the sensing electrode to enable an indication whether the sensor is operating correctly.

Claims

1. A gas sensor, comprising:

a housing having disposed therein;

at least one sensing electrode;

at least one counter electrode;

at least one test electrode; and

at least one electrolyte in contact with at least one of said at least one sensing electrode, said at least one counter electrode and said at least one test electrode;

wherein said housing permits at least a gas to be sensed to flow from an environment to said at least one sensing electrode;

wherein said gas sensor is operable in a normal mode of operation in which said gas sensor detects whether said gas to be sensed is present at said at least one sensing electrode, and in a test mode of operation in which said at least one test electrode generates a test gas which flows to said at least one sensing electrode to enable an indication whether said gas sensor is operating correctly;

wherein at least two of said at least one sensing electrode, said at least one counter electrode and said at least one test electrode are mounted side-by-side on a same side of a common porous gas permeable substrate to define a planar electrode assembly; and

wherein said at least one sensing electrode and said at least one test electrode are mounted side-by-side on the same side of said common porous gas permeable substrate and are in contact with a common electrolyte.

2. The gas sensor according to claim 1, further comprising:

at least one reference electrode,

wherein said at least one counter electrode, said at least one reference electrode, said at least one sensing electrode and said at least one test electrode are mounted side-by-side on the same side of said common porous gas permeable substrate, and are in contact with a common electrolyte.

3. The gas sensor according to claim 1, wherein:

said at least one test electrode is arranged and positioned relative to said at least one sensing electrode so that gas generated by said at least one test electrode is released into a communicating space in the vicinity of said at least one sensing electrode.

4. The gas sensor according to claim 1, further comprising:

a diffusion barrier through which gas generated by said at least one test electrode diffuses to reach said at least one sensing electrode.

5. The gas sensor according to claim 1, wherein:

said common porous gas permeable substrate is a flexible gas permeable membrane that is impermeable to electrolytes.

6. The gas sensor according to claim 1, wherein:

said sensing electrode occupies a central region of said common porous gas permeable substrate, said at least one test electrode being separated from said at least one sensing electrode by a narrow first channel, and

wherein said at least one counter electrode is located adjacent said at least one sensing electrode and is electrically separated from said sensing electrode by at least a second channel.

7. The gas sensor according to claim 1, wherein:

said housing comprises;

a cap having a diffusion hole communicating with a manifold recess adjacent said at least one sensing electrode, an edge of said manifold recess being located between said at least one sensing electrode and said at least one test electrode.

8. The gas sensor according to claim 1, wherein:

said at least one sensing electrode is generally rectangular and has two projections forming electrical contacts,

wherein said at least one counter electrode is provided adjacent, and on the same side of said common permeable substrate as said at least one sensing electrode.

9. The gas sensor according to claim 1, wherein:

a shape of said at least one sensing electrode has a recess, and

wherein said at least one test electrode is located in said recess, separated by a U-shaped channel, said at least one test electrode being located in a center of said sensing electrode, said at least one test electrode having a contact strip extending from said at least one test electrode to an electrical terminal means, said contact strip being insulated from said at least one electrolyte.

10. The gas sensor according to claim 1, further comprising:

blockage means for preventing flow of gas generated by said test electrode, and thereby forcing said gas generated by said test electrode to flow through said at least one electrolyte to reach said at least one sensing electrode.

11. The gas sensor according to claim 1, further comprising:

a manifold; and

a control circuitry,

wherein said at least one test electrode comprises;

a first gas generator electrode; and

a second gas generator electrode,

wherein said manifold is shared by said first gas generator electrode and said at least one sensing electrode, said manifold allowing a first test gas generated by said first gas generator electrode to reach said at least one sensing electrode therethrough,

wherein said second gas generator electrode does not share said manifold with said at least one sensing electrode, a second test gas generated by said second gas generator electrodes flowing through said at least one electrolyte to reach said at least one sensing electrode, and

wherein said control circuitry is operable to control said first gas generator electrode and said second gas generator electrode in accordance with a test sequence.

12. The gas sensor according to claim 1, further comprising:

a valve means for closing said housing to said environment during a self testing.

13. A gas sensor, comprising:

a housing having disposed therein;

at least one sensing electrode;

at least one counter electrode;

at least one test electrode; and

at least one electrolyte in contact with at least one of said at least one sensing electrode, said at least one counter electrode and said at least one test electrode;

wherein said housing permits at least a gas to be sensed to flow from an environment to said at least one sensing electrode;

wherein said gas sensor is operable in a normal mode of operation in which said gas sensor detects whether said gas to be sensed is present at said at least one sensing electrode, and in a test mode of operation in which said at least one test electrode generates a test gas which flows to said at least one sensing electrode to enable an indication whether said gas sensor is operating correctly;

wherein at least two of said at least one sensing electrode, said at least one counter electrode and said at least one test electrode are mounted side-by-side on a same side of a common porous gas permeable substrate to define a planar electrode assembly; and

wherein said at least one sensing electrode and said at least one test electrode are mounted side-by-side on the same side of said common porous gas permeable substrate and are in contact with separate electrolytes.

14. The gas sensor according to claim 13, further comprising:

at least one reference electrode.

15. The gas sensor according to claim 14, wherein:

said at least one counter electrode, said at least one sensing electrode, said at least one reference electrode, and said at least one test electrode are mounted side-by-side on the same side of the common porous gas permeable substrate.

16. The gas sensor according to claim 14, comprising:

at least two counter electrodes.