Measuring cell for an electrochemical gas sensor

• US 4,988,429 A
• Filed: 06/22/1990
• Issued: 01/29/1991
• Est. Priority Date: 06/30/1989
• Status: Expired due to Fees

• Current Assignee: Dragerwerk AG
• Original Assignee: Dragerwerk AG
• Inventors: Matthiessen, Hans
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/544,107
• Time in Patent Office: 221 Days
• Field of Search: 204/408, 204/415
• US Class Current: 204/408
• CPC Class Codes: G01N 27/404 Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid , e.g. Clark-type oxygen sensors
• CPC Class Codes: G01N 27/4045 for gases other than oxygen

Abstract

The invention is directed to a measuring cell for an electrochemical gas sensor having an electrolytic chamber and a measuring electrode as well as a counter electrode. In the direction facing the ambient, the measuring electrode includes a diffusion membrane as well as a diffusion barrier. The diffusion barrier is made of a material which is a good conductor of heat and is provided with a plurality of passages. A temperature-sensitive element is provided in the immediate proximity of these passages and faces toward the ambient. With this configuration, the temperature dependency of the diffusion capacity of the gas sample passing through the diffusion barrier can be included in the processing of the signal indicative of the measurement.

Claims

1. A measuring cell for an electrochemical gas sensor for detecting a gaseous substance, the measuring cell comprising:

a housing having an opening directed toward the sample to be measured and defining an electrolyte chamber;

an electrolyte contained in said chamber;

a measuring electrode and a counter electrode disposed in said chamber so as to be in spaced relationship to each other;

a porous membrane mounted in said housing for separating said chamber from the ambient to be investigated and to contain said electrolyte in said chamber;

said membrane being permeable to the gaseous substance to be detected;

a diffusion barrier made of a material having a good thermal conductivity and being mounted in said housing so as to be interposed between the ambient and said membrane;

said diffusion barrier having a surface facing the ambient and having passage means formed therein for passing the gaseous substance to said porous membrane; and

,

temperature-sensitive means formed on said surface in close proximity to said passage means for detecting the temperature where the gaseous substance diffuses through the diffusion barrier.

2. The measuring cell of claim 1, said passage means being a plurality of passages extending through said diffusion barrier;

and, said temperature-sensitive means being a strip-shaped layer applied to said surface of said diffusion barrier so as to define a path guided around said passages.

3. The measuring cell of claim 2, said diffusion barrier being made of ceramic.

4. The measuring cell of claim 1, said passage means being a plurality of passages extending through said diffusion barrier;

and, said temperature-sensitive means being a layer applied to said surface of said diffusion barrier so as to cover over at least a portion of said passages; and

, said layer having breakthroughs formed therein so as to be in alignment with the passages of said portion of said passages.

5. The measuring cell of claim 4, said diffusion barrier being made of ceramic.

6. The measuring cell of claim 1, said diffusion barrier being made of ceramic and said temperature-sensitive means being a temperature-sensitive layer applied to said surface of said diffusion barrier.

7. The measuring cell of claim 1, said diffusion barrier being made of metal;

and, said temperature-sensitive means including;

an intermediate electrically-insulating layer applied to said surface of said diffusion barrier; and

, temperature-sensitive layer means applied to said electrically-insulating layer.