Gas sensor

• US 20060162426A1
• Filed: 10/05/2005
• Published: 07/27/2006
• Est. Priority Date: 01/22/2005
• Status: Active Grant

• Current Assignee: Draeger Safety Incorporated (Dragerwerk AG)
• Original Assignee: Draeger Safety Incorporated (Dragerwerk AG)
• Inventors: Haack, Nils, Lange, Bjorn, Chrzan, Rigobert, Wulf, Lars
• Granted Patent: US 7,406,854 B2
• Time in Patent Office: Days
• US Class Current: 73/31.50
• CPC Class Codes: G01N 21/09 adapted to resist hostile environments or corrosive or abrasive materials
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis
• CPC Class Codes: G01N 27/16 caused by burning or catalytic oxidation of surrounding material to be tested, e.g. of gas
• CPC Class Codes: G01N 33/0006 Calibrating gas analysers

Abstract

A gas sensor is provided that is delimited from the environment with a preferably replaceable cap (8) made of a porous, gas-permeable and water-impermeable material, especially sintered PTFE. The gas sensor is protected against environmental moisture and can be permanently provided with the cap (8) and with a special calibrating adapter (9) both during the gas measurement and during the necessary calibration. Due to the special design of the cap (8) and the calibrating adapter (9), the gas sensor offers the possibility of remote calibration, which can be carried out with high accuracy and is independent from weather effects, especially wind.

Claims

1. A gas sensor, comprising:

a measuring element, which generates a measured signal that depends on the concentration of a measured gas;

a cap to delimit the gas sensor from the environment, the cap being made of a porous, gas-permeable and water-impermeable material.

2. A gas sensor in accordance with claim 1, further comprising a calibrating adapter having a gas admission pipe connection for supplying a calibrating gas to the cap of the gas sensor, said calibrating adapter being attached to or screwed on the cap.

3. A gas sensor in accordance with claim 2, wherein the cap and the calibrating adapter are designed such that they can be replaced individually or together.

4. A gas sensor in accordance with claim 2, wherein the cap and the calibrating adapter are designed as a one-piece component.

5. A gas sensor in accordance with claim 1, wherein the cap consists essentially of PTFE (polytetrafluoroethylene) or hydrophobized PE (polyethylene).

6. A gas sensor in accordance with claim 1, wherein the cap comprises a sintered PTFE (polytetrafluoroethylene) or sintered hydrophobized PE (polyethylene) with a pore volume of about 30% to 70%.

7. A gas sensor in accordance with claim 1, wherein the gas sensor is an infrared optical gas sensor and the measuring element includes an infrared detector.

8. A gas sensor in accordance with claim 1, wherein the gas sensor is an electrochemical gas sensor and the measuring element is a measuring electrode.

9. A gas sensor in accordance with claim 1, wherein the gas sensor is a catalytic heat tone sensor and the measuring element is a pellistor.

10. A gas sensor in accordance with claim 1, wherein the cap is white.

11. A gas sensor in accordance with claim 1, wherein a porous, sintered metal body is arranged as an explosion protection means between said measuring element and said cap.

12. A gas sensor in accordance with claim 2, wherein said cap has a smaller layer thickness and/or a higher porosity in an area of the gas admission pipe connection than in a remaining area.

13. A gas sensor in accordance with claim 2, further comprising a cuvette heater in an area of the gas admission pipe connection of the calibrating adapter.

14. A gas sensor in accordance with claim 2, wherein said cap and said calibrating adapter are connected to the gas sensor both during the use for measurement and during the calibration.

15. A gas sensor in accordance with claim 2, wherein a flow resistance of the material of the cap is selected to be such that the pressure in the measuring cell exceeds the dynamic pressure of wind impinging on an outer side of said cap with the calibrating adapter during the calibration by means of calibrating gas fed in.

16. A gas sensor in accordance with claim 2, wherein due to the geometry of the calibrating adapter and the flow resistance of the material of the cap, the diffusion of measured gas to the measuring element is hindered only to the extent that the response time of the gas sensor during the gas measurement is prolonged by less than 30% compared to the operation without said calibrating adapter and said cap.

17. A gas sensor in accordance with claim 2, wherein a flow resistance of the material of the cap is selected to be such that the overpressure generated in the measuring cell by a calibrating gas flow through the gas admission pipe connection does not exceed 50 hPa.