Electrochemical gas sensor

• US 5,273,640 A
• Filed: 06/05/1991
• Issued: 12/28/1993
• Est. Priority Date: 06/11/1990
• Status: Expired due to Fees

• Current Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Inventors: Inoue, Takahiro, Kusanagi, Sigekazu, Watabe, Yoshifumi, Fujioka, Toru, Doi, Kenji, Yamaga, Noriyuki
• Primary Examiner(s): TUNG, TA HSUNG
• Application Number:
  US07/710,339
• Time in Patent Office: 937 Days
• Field of Search: 204/153.1, 204/153.17, 204/153.18, 204/400, 204/401, 204/412, 204/415, 204/421-429, 204/153.19, 204/153.2
• US Class Current: 204/401
• CPC Class Codes: G01N 27/4175 Calibrating or checking the analyser
• CPC Class Codes: G01N 33/007 Arrangements to check the analyser calibrating G01N33/0006

Abstract

An electrochemical gas sensor includes, as disposed on an insulating substrate, a plurality of electrodes for individually sensing a standard gas present in a surrounding atmosphere at a fixed concentration and a target gas present in the surrounding atmosphere, and a signal processing circuit for determining sensor life on the basis of sensed outputs of the standard gas. Constant detection of the sensitivity characteristics of the gas sensor is thereby attained for self-examination of the life thereof.

Claims

1. An electrochemical gas sensor comprising:

an insulating substrate;

a gas sensing section including a first electrode set comprising a working electrode, a counter electrode, and a reference electrode mutually separated form each other and disposed on the insulating substrate, and a solid electrolyte layer on the insulating substrate and covering the electrode set;

gas detecting means connected to the electrode set for applying to the working electrode an electric potential varying at predetermined time intervals between a first level for detecting a toxic gas in an ambient in which the sensor is used and a second level for detecting oxygen in the ambient and generating an output signal indicating toxic gas level or oxygen gas level in the ambient; and

determining means connected to the gas detecting means for determining when gas sensing section sensitivity to the toxic gas has fallen below a predetermined level on the basis of the output signal of the gas detecting means when the potential has the second level.

2. An arrangement as claimed in claim 1 wherein the detecting means determines that the sensitivity of the gas sensing section to the toxic gas has fallen below a predetermined level when the output signal of the gas detecting means fails to indicate the presence of oxygen at a constant concentration in the ambient when the potential is at the second level.

3. An electrochemical gas sensor comprising:

an insulating substrate;

p1 a first gas sensing section including a first electrode set comprising a working electrode, a counter electrode, and a reference electrode mutually separated form each other an disposed on the insulating substrate, and a solid electrolyte layer on the insulating substrate and covering the first electrode set;

a second gas sensing section including a second electrode set comprising a working electrode, a counter electrode, and a reference electrode mutually separated from each other and disposed on the insulating substrate, and a solid electrolyte layer on the insulating substrate covering the second electrode set the working electrode, the counter electrode, the reference electrode, and the solid electrolyte layer of the second gas sensing section comprising the same material as the working electrode, the counter electrode, the reference electrode, and the solid electrolyte layer, respectively, of the first gas sensing section;

gas detecting means connected to the first and second electrode sets for applying to the working electrode of the first electrode set an electric potential varying with a first timing between a first level for detecting a toxic gas in an ambient in which the sensor is used and a second level for detecting oxygen in the ambient and applying to the working electrode of the second electrode set an electric potential varying between the first level and the second level with a second timing different from the first timing and generating an output signal indicating toxic gas level and oxygen gas level in the ambient; and

determining means connected to the gas detecting means for determining when first gas sensing section sensitivity to the toxic gas has fallen below a predetermined level on the basis of the output signal of the gas detecting means when the potential applied to the working electrode of the first electrode set has the second level.

4. An electrochemical gas sensing arrangement comprising:

an insulating substrate;

a toxic gas sensing section comprising a first electrode set disposed on the insulating substrate for exposure to an ambient containing a constant concentration of oxygen, said first electrode set comprising working, counter, and reference electrodes mutually separated from each other and a solid electrolyte layer on the substrate covering the first electrode set;

an oxygen gas sensing section comprising a second electrode set disposed on the insulating substrate for exposure to the ambient, the second electrode set comprising working, counter, and reference electrodes mutually separated from each other, and a solid electrolyte layer on the substrate covering the second electrode set, the solid electrolyte layer of the oxygen gas sensing section comprising the same material as the solid electrolyte layer of the toxic gas sensing section;

toxic gas sensing means connected to the toxic gas sensing section for sensing toxic gas level in the ambient and generating an output signal indicating the sensed toxic gas level;

oxygen gas sensing means connected to the oxygen gas sensing section for sensing oxygen level in the ambient and generating an output signal indicating the sensed oxygen level; and

alarm means connected to the oxygen gas sensing means for generating an alarm indicating that toxic gas sensing section sensitivity has fallen below a predetermined level in response to the output signal of the oxygen gas sensing means.

5. The sensor according to claim 4 comprising correcting means connected to said oxygen gas sensing means for correcting the output signal of said toxic gas sensing means in response to the output signal of said oxygen ga sensing means.

6. The sensor according to claim 5 wherein said correcting means comprises means for correcting the output signal of said toxic gas sensing means in accordance with humidity of the ambient.

7. The sensor according to claim 5 wherein said correcting means comprises means for correcting the output signal of said toxic gas sensing means in accordance with temperature of the ambient.

8. An arrangement as claimed in claim 4 wherein the alarm means comprises means for generating the alarm when the output signal of the oxygen gas sensing means falls below a predetermined level.

9. An arrangement as claimed in claim 8 wherein the predetermined level corresponds to a constant concentration of oxygen present in the ambient.

10. An arrangement as claimed in claim 4 wherein the toxic gas sensing section is separated from the oxygen gas sensing section.