Gas sensor

• US 4,839,020 A
• Filed: 05/22/1987
• Issued: 06/13/1989
• Est. Priority Date: 05/26/1986
• Status: Expired due to Term

• Current Assignee: Terumo Kabushiki Kaisha
• Original Assignee: Terumo Kabushiki Kaisha
• Inventors: Yamaguchi, Shuichiro, Shimomura, Takeshi, Daikuhara, Norio
• Primary Examiner(s): Kalafut, Stephen J.
• Application Number:
  US07/053,280
• Time in Patent Office: 753 Days
• Field of Search: 204/414, 204/424, 204/431, 204/433
• US Class Current: 204/431
• CPC Class Codes: G01N 27/4035 Combination of a single ion-sensing electrode and a single reference electrode G01N27/406 and G01N27/413 take precedence

Abstract

A gas sensor includes a multi-layered solid-state pH electrode and a reference electrode coated with a gas-sensitive layer (solid-state or gel-state) sensitive to an ion of interest, the surface of the combination being coated with a gas-permable layer. Also provided in a gas sensor having a pH electrode and a reference electrode immersed in a gas-sensitive solution within a gas-permeable layer. Preferably, a fixed distance is maintained between a sensitive portion of the pH electrode, a sensitive portion of the reference electrode and the gas-permeable layer isolated by means of a porous layer. In another emodiment, the gas sensor incorporates a common electrode and a thermister for temperature calibration.

Claims

1. A gas sensor comprising:

a pH electrode which includes an electrically conductive substrate, a redox layer coating a surface of said electrically conductive substrate, and a hydrogen ion carrier layer coating a surface of said redox layer;

a reference electrode;

an insulating layer for insulating said pH electrode and said reference electrode;

a gas-sensitive layer coating exposed surface portions of said pH electrode, said insulating layer and said reference electrode; and

a gas-permeable layer coating a surface of said gas-sensitive layer.

2. The gas sensor according to claim 1, wherein said reference electrode comprises a silver having a silver chloride formed on a surface thereof.

3. The gas sensor according to claim 1, wherein said gas-sensitive layer comprises an aqueous solution of polyvinyl alcohol dissolved in a solvent which contains a salt derived from the interest gas.

4. The gas sensor according to claim 1, wherein said gas-permeable layer comprises a silicone membrane.

5. A gas sensor comprising:

a pH electrode having a sensitive portion;

a reference electrode having a sensitive portion; and

a gas-permeable layer contacting the sensitive portion of said pH electrode and the sensitive portion of said reference electrode through the intermediary of a gas-sensitive solution or gel;

said pH electrode further comprising;

an electrically conductive substrate;

a redox layer coating a surface of said electrically conductive substrate; and

a hydrogen ion carrier layer, which is sensitive to a hydrogen ion concentration, coating said redox layer.

6. The gas sensor according to claim 5, further comprising a porous layer for maintaining a constant spacing between the sensitive portion of said pH electrode and said gas-permeable layer.

7. The gas sensor according to claim 5, wherein said reference electrode comprises:

an agar-agar gel containing saturated sodium chloride partitioned by at least two barrier walls penetrated by a hollow fiber, and

a silver/silver chloride electrode in said agar-agar gel.

8. The gas sensor according to claim 5, wherein said gas-sensitive solution comprises an aqueous solution of polyvinyl chloride dissolved in a solvent which contains a salt derived from the interest gas.

9. The gas sensor according to claim 5, wherein said gas-permeable layer comprises a silicone membrane.

10. A gas sensor comprising:

a pH electrode having a sensitive portion;

a reference electrode having a sensitive portion;

a thermistor; and

a gas-permeable layer contacting the sensitive portion of said pH electrode, the sensitive portion of said reference electrode and said thermister through the intermediary of a gas-sensitive solution;

said pH electrode further comprising;

an electrically conductive substrate;

a redox layer coating a surface of said electrically conductive substrate; and

a hydrogen ion carrier layer, which is sensitive to a hydrogen ion concentration, coating said redox layer.

11. The gas sensor according to claim 10, wherein said pH electrode further comprising a porous layer for maintaining a constant spacing between the sensitive portion of said pH electrode and said gas-permeable layer.

12. The gas sensor according to claim 10, wherein said reference electrode comprises:

an agar-agar gel containing saturated sodium chloride partitioned by at least two barrier walls penetrated by a hollow fiber, and

a silver/silver chloride electrode in said agar-agar gel.

13. The gas sensor according to claim 10, wherein said gas-sensitive solution comprises an aqueous solution of polyvinyl chloride dissolved in a solvent which contains a salt derived from the interest gas.

14. The gas sensor according to claim 10, wherein said gas-permeable layer comprises a silicone film.