Electrochemical gas sensor

• US 20060124458A1
• Filed: 09/22/2005
• Published: 06/15/2006
• Est. Priority Date: 12/09/2004
• Status: Active Grant

• Current Assignee: Draeger Safety Incorporated (Dragerwerk AG)
• Original Assignee: Draeger Safety Incorporated (Dragerwerk AG)
• Inventors: Chrzan, Rigobert, Dietrich, Michael, Bernstein, Christoph, Sick, Michael, Busack, Hans-Jurgen, Kruger, Dieter, Nauber, Andreas, Hermann, Kathrin
• Granted Patent: US 7,608,177 B2
• Time in Patent Office: Days
• US Class Current: 204/424
• 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: Y02E 60/36 Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Abstract

An electrochemical gas sensor with a stacked arrangement of electrodes and nonwoven layers arranged in parallel, comprising at least one measuring electrode (3) and at least one counterelectrode (5). A porous membrane (8) that is permeable to air is in contact with the stacked arrangement of electrodes and nonwoven layers arranged in parallel at least on one side, at least one layer of a hydrophilic nonwoven (7) is located between the electrodes. The porous membrane (8) that is permeable to air and the hydrophilic nonwoven (7) extend into a separate equalization volume (9), which is filled with electrolyte at least partially and is located at least partially in one plane with the electrodes. The separate equalization volume (9) surrounds the electrode arrangement at least partially in this plane, and the porous membrane (8) that is permeable to air is exposed to ambient pressure at least in partial areas. Such sensors are characterized by a flat shape, high insensitivity to shocks, independence from the position, and high tolerance to variations in environmental humidity.

Claims

1. An electrochemical gas sensor, comprising:

at least one measuring electrode;

at least one counterelectrode;

a nonwoven layer, said at least one measuring electrode and said at least one counterelectrode cooperating with said nonwoven layer to form a stacked arrangement of electrodes and nonwoven layer arranged in parallel with said nonwoven layer being a hydrophilic nonwoven material layer arranged between said electrodes;

a porous membrane, that is permeable to air, in contact on at least one side with said stacked arrangement of said electrodes and nonwoven layer arranged in parallel;

a separate equalization volume filled with electrolyte at least partially, said porous membrane that is permeable to air and said hydrophilic nonwoven material layer extending into said separate equalization volume filled with electrolyte at least partially, said separate equalization volume being located at least partially in a plane with said electrodes and surrounding said electrode arrangement at least partially in the plane, said porous membrane that is permeable to air being exposed to ambient pressure at least in partial areas.

2. A sensor in accordance with claim 1, wherein said counterelectrode is applied to said porous membrane that is permeable to air.

3. A sensor in accordance with claim 1, wherein said equalization volume surrounds the electrode arrangement along a closed figure.

4. A sensor in accordance with claim 1, wherein said porous membrane that is permeable to air consists of PTFE.

5. A sensor in accordance with claim 1, wherein said electrodes, said hydrophilic nonwoven and said porous membrane that is permeable to air occupy each essentially a circular area, wherein said porous membrane that is permeable to air has strips, which are arranged in a star-shaped pattern and extend from the edge of the circular area into said equalization volume.

6. A sensor in accordance with claim 5, wherein said hydrophilic nonwoven has strips which are arranged in a star-shaped pattern and extend from the edge of the circular area into said equalization volume, wherein the end of at least one of said strips is immersed into the electrolyte in said equalization volume.

7. A sensor in accordance with claim 1, wherein said hydrophilic nonwoven and said porous membrane that is permeable to air have at least three strips each that are arranged in a star-shaped pattern and extend from the edge of the circular area into said equalization volume.

8. A sensor in accordance with claim 7, wherein said hydrophilic nonwoven and said porous membrane that is permeable to air have said strips each that are arranged in a star-shaped pattern and extend from the edge of the circular area into said equalization volume.

9. A sensor in accordance with claim 1, further comprising a filter filtering gases that reach said porous membrane that is permeable to air from the atmosphere surrounding the sensor.

10. A sensor in accordance with claim 9, wherein said filter is protected on a side exposed of the atmosphere by a cover, through which leads an opening that determines the inlet of gas.

11. A sensor in accordance with claim 10, wherein said cover is a name or indicia plate with a label characterizing the sensor.

12. A sensor in accordance claim 1, wherein said electrode arrangement contains at least one reference electrode embedded between said measuring electrode and said counterelectrode and embedded in said hydrophilic nonwoven on both sides and has an area that is smaller than the area of said measuring electrode and smaller than the area of said counterelectrode.

13. A sensor in accordance claim 1, further comprising a diffusion-inhibiting membrane arranged between said measuring electrode and said counterelectrode.

14. A sensor in accordance with claim 13, wherein said diffusion-inhibiting membrane has a weaker barrier action against ions than against neutral species.

15. A sensor in accordance claim 1, wherein said stacked arrangement of electrodes and nonwoven layer and said air-permeable membrane is surrounded by a two-part housing, with said two parts connected to one another by a snap connection, said two parts being shaped such that said stacked arrangement of electrodes and nonwoven layer and said air-permeable membrane is fixed in a non-positive manner.

16. A sensor in accordance with claim 15, wherein the contact area between said housing parts has an electrolyte-proof liquid seal.

17. A sensor in accordance with claim 12, wherein said stacked arrangement of electrodes includes a reference electrode comprising a sintered mixture of a metal and its metal oxide from the platinum group, the iridium group or gold.

18. A sensor in accordance with claim 17, wherein said stacked arrangement of electrodes includes a reference electrode comprising doped diamond or diamond-like carbon.

19. A sensor in accordance claim 1, further comprising readable means for storing sensor-specific data.

20. A sensor in accordance with claim 19, wherein said readable means for storing sensor-specific data comprises at least one EEPROM or a transponder.

21. A sensor in accordance with claim 19, wherein said readable means for storing sensor-specific data are set up to store type information and/or information on the sensitivity of the sensor and/or on a performed gauging and/or calibration and/or information relevant for approval.

22. A sensor in accordance claim 1, wherein said measuring electrode comprises a plurality of measuring electrode sectors separated from one another electrically and each comprising a different electrode material.

23. A sensor in accordance claim 1, wherein said sensor housing has a gas inlet opening for the entry of the gas to be measured, which communicates with the environment of the sensor via a pneumatic damping element.

24. A sensor in accordance claim 1, wherein said electrodes and/or a readable means for storing sensor-specific data are contacted via contact pins that can be inserted into said sensor housing and are in firm contact in the inserted state with said conductive connection means, which lead to said electrodes and/or said readable means for storing sensor-specific data and are electrically connected to these.

25. A sensor in accordance with claim 24, wherein said conductive connection means, which lead from the side of said contact pins that can be inserted into said sensor housing to said electrodes and/or to said readable means for storing sensor-specific data, comprise wires that lead at least partially through a liquid seal.