Method and device for identifying gaseous compounds

• US 6,636,811 B1
• Filed: 10/24/2000
• Issued: 10/21/2003
• Est. Priority Date: 02/24/1998
• Status: Expired due to Term

• Current Assignee: WMA Airsense Analysentechnik GmbH
• Original Assignee: WMA Airsense Analysentechnik GmbH
• Inventors: Dohren, Stefan, Matz, Gerhard, Walte, Andreas, Hunte, Torsten, Munchmeyer, Wolf
• Primary Examiner(s): Hoff, Marc S.
• Assistant Examiner(s): SUAREZ, FELIX E
• Application Number:
  US09/623,118
• Time in Patent Office: 1,092 Days
• Field of Search: 702/22, 702/23-25, 702/30, 702/100, 702/116, 702/120, 702/126, 422/63, 422/69, 435/320, 204/603
• US Class Current: 702/24
• CPC Class Codes: G01N 33/0031 comprising two or more sensors, e.g. a sensor array

Abstract

The invention relates to a device for identifying gaseous compounds, comprising a sensor array (1) having, for instance, ten gas sensors (2) in the form of semiconductor gas sensors. Said sensor array (1) has a supply line (3) with an inlet (4) and an outlet (5). A switchable three-way valve (6) is located in the supply line (3), to which a selective collector unit (7) is attached. Said collector unit (7) comprises a special adsorber (8), a heater (9) and a separate feed pump (10) with a flow sensor (11). A secondary line (12), in which a dilution unit (13) is arranged, discharges into the feed line (3) between the three-way valve (6) and the sensor array (1). A feeding and control unit (16) also having a feed pump (17) with a flow sensor (18) is located in the area of the outlet (5) of the sensor array (1). An electrical line (19) leading to an evaluation computer (20) branches off from the sensor array (1).

Claims

1. Method for determining gaseous compounds, wherein a sample gas stream is lead to a sensor array (1) with several gas sensors (2), wherein the electrical output signal of the individual gas sensors (2) are captured by the evaluation computer (20), wherein the electrical output signals are converted into a characterizing image, are stored and are compared with the images of other gas mixtures,

characterized in that the sample gas stream is thinned with a stream of air prior to the feeding into the sensor array (1) and wherein thereby the concentration of the sample gas stream is kept constant to a predetermined value below the saturation concentration.

2. Method for determining gaseous compounds,

wherein a sample gas stream is lead to a sensor array (1) with several gas sensors (2), wherein the electrical output signal of the individual gas sensors (2) are captured by the evaluation computer (20), wherein the electrical output signals are converted into a characterizing image, are stored and are compared with the characterizing images of other gas mixtures,

characterized in that the sample gas stream is thinned with a stream of air prior to the feeding into the sensor array (1) and wherein thereby the concentration of the sample gas stream kept constant to a predetermined value below the saturation concentration,

wherein the sample gas stream contains easily volatile gas components and wherein the sample gas stream is separated and is freed of easily volatile gas components prior to the feeding into the sensor array (1) and prior to the mixing with the air stream.

3. Method according to claim 2, wherein the sample gas stream contains easily volatile gas components, medium volatile gas components and hardly volatile components and wherein the medium and hardly volatile gas components of the sample gas stream are separated from the easily volatile gas components of the sample gas stream by adsorption and in the following the enriched gas components are released by thermal desorption.

4. Apparatus for determining a gaseous compound, comprising a sensor array (1) with several gas sensors (2) and a transfer and control unit (16) for the controlled transport of a sample gas stream through the sensor array (1) as well as a bypass connected evaluation computer (20) for capturing all signals of the sensor array (1) and for converting the signals into a characterizing image of the sample gas stream and for storing this characterizing image, characterized in that a switchable three way valve (6) is disposed in a feed line (3) with an inlet port (4) of the sensor array (1), wherein the switchable three way valve (6) is in connection with a selective collection unit (7) and wherein a sideline (12) with a thinning unit (13) joins between the three way valve (6) and the sensor array (1).

5. Apparatus according to claim 4, characterized in that the selective collection unit (7) is equipped with an automatically controllable feed transport pump (10) reversible in its transport direction.

6. Apparatus according to claim 5, characterized in that the selective collection unit (7) comprises an adsorber (8) and a heater (9).

7. Apparatus according to claim 4, characterized in that the thinning unit (13) comprises an automatically controllable feed transport pump (14) and an air filter.

8. Method for determining gaseous compounds, wherein a sample gas stream is lead to a sensor array (1) with several gas sensors (2), wherein the electrical output signals of the individual gas sensors (2) are captured by the evaluation computer (20), wherein the electrical output signals are converted into a characterizing image, are stored and are compared with the characterizing images of other gas mixtures, characterized in that the sample gas stream possibly contains easily volatile gas components, wherein the sample gas stream is separated and freed of easily volatile gas components and in the following is thinned with a stream of air prior to the feeding into the sensor array (1) and wherein thereby the concentration of the sample gas stream is kept constant to a predetermined value below the saturation concentration for obtaining a comparable characterizing image.

9. Method according to claim 8, characterized in that the medium and hardly volatile gas components of the sample gas stream are separated from the easily volatile gas components of the sample gas stream by adsorption and in the following the enriched gas components are released by thermal desorption.

10. Apparatus for determining of gaseous compound, comprising a sensor array (1) with the several gas sensors (2) and the transfer and control unit (16) for the controlled transport of a sample gas stream through the sensor array (1) as well as a bypass connected evaluation computer (20) for capturing all signals of the sensor array (1) and for converting the signals into a characterizing image of the sample gas stream and for storing this characterizing image,

characterized in that a switchable three-way valve (6) is disposed in a feed line (3) with an inlet port (4) of the sensor array (1), wherein the switchable three-way valve (6) is in connection with a selective collection unit (7) for separating and freeing of easily volatile gas components and wherein a sideline (12) with a thinning unit (13) joins between the three way valve (6) and the sensor array (1) for maintaining the concentration of the sample gas stream constant at a predetermined value below the saturation concentration.

11. Apparatus according to claim 10, characterized in that the selective collection unit (7) is equipped with an automatically controllable feed transport pump (10) reversible in its transport direction.

12. Apparatus according to claim 11, characterized in that the selective collection unit (7) comprises an adsorber (8) and a heater (9) as well as a separate feed transport pump (10) with a flow sensor (11) for the feed transport pump (10).

13. Apparatus according to claim 11, characterized in that the thinning unit (13) comprises an automatically controllable feed transport pump (14), a flow sensor (15) for the feed transport pump (14), and the air filter.

14. A method for determining gaseous compounds comprising the steps:

separating and freeing a sample gas stream of easily volatile gas components;

thinning the sample gas stream with a stream of air prior to a feeding into a sensor array (1);

leading the sample gas stream to the sensor array (1) with several gas sensors (2);

capturing individually electrical output signals of the gas sensors (2) with an evaluation computer (20);

converting the electrical output signals into a characterizing diagram;

storing the characterizing diagram;

comparing the characterizing diagram with diagrams of other gas mixtures;

keeping thereby the concentration of the sample gas stream constant to a predetermined value below a saturation concentration for obtaining a comparable characterizing diagram.

15. The method according to claim 14, further comprising separating medium volatile gas components and hardly volatile gas components of the sample gas stream from the easily volatile gas components of the sample gas stream by adsorption;

and releasing the enriched gas components by thermal desorption thereafter.

16. The method according to claim 14 further comprising the step:

fixing a work point of the gas sensor (2) in a lower region of a nonlinear concentration curve of the gas sensor (2) for obtaining a most sensitive response of the gas sensor (2) and a quickest response of the gas sensor(2).

17. The method according to claim 14 further comprising the step:

thinning the sample gas stream with fresh air for linearizing the characterizing curves of the individual gas sensors.

18. The method according to claim 14 further comprising the step:

comparing measurements with characterizing images of a gas mixture with high precision and independent of concentration with the evaluation computer (20).

19. The method according to claim 14 further comprising the step:

continuously monitoring the mixing process by the evaluation computer (20);

continuously regulating the mixing process by the evaluation computer (20);

optically imaging the characterizing diagram of a gas compound by the evaluation computer (20).

20. An apparatus for determining of a gaseous compound, comprising

several gas sensors (2) forming a sensor array (1);

a feed line (3) with an inlet port (4) connected to the sensor array (1);

a transfer and control unit (16) for a controlled transport of a sample gas stream through the sensor array (1);

an evaluation computer (20) connected as a bypass for capturing all signals of the sensor array (1) and for converting the signals into a characterizing diagram of the sample gas stream and for storing this diagram;

a switchable three-way valve (6) disposed in the feed line (3) of the sensor array (1);

a selective collection unit, wherein the switchable three-way valve (6) is in connection with the selective collection unit (7) for separating and freeing of easily volatile gas components;

a thinning unit (13);

a sideline (12) with the thinning unit (13) joining between the switchable three-way valve (6) and the sensor array (1) for maintaining the concentration of the sample gas stream constant at a predetermined value below the saturation concentration.

21. The apparatus according to claim 20 further comprising

an automatically controllable feed transport pump (10) reversible in its transport direction furnished to the selective collection unit (7).

22. The apparatus according to claim 20 further comprising

an adsorber (8) furnished at the selective collection unit (7);

a heater (9) furnished at the selective collection unit (7);

a separate feed transport pump (10) furnished at the selective collection unit (7);

a flow sensor (11) furnished to the feed transport pump (10).

23. The apparatus according to claim 20 further comprising

an automatically controllable feed transport pump (14) furnished to the thinning unit (13);

a flow sensor (15) furnished to the thinning unit (13) for connection to the feed transport pump (14);

an air filter furnished to the thinning unit (13).

24. The apparatus according to claim 20, wherein the sensor array (1) includes a semiconductor gas sensor.

25. The apparatus according to claim 20, wherein the evaluation computer (20) controls a switchable three way valve (6) for controlling the sample gas stream, which sample gas stream is lead over the selective collection unit or passed by the selective collection unit as desired.

26. The apparatus according to claim 20 further comprising an outlet port (5) connected to the transfer and control unit (16).

27. The apparatus according to claim 20, wherein the evaluation computer (20) is connected to flow sensors (11, 15, 18) through connection lines.

28. The apparatus according to claim 20 further comprising a feed transport pump (17) of the transport and control unit (16), wherein the feed transport pump (17) sucks in a predetermined flow of the gas mixture through the inlet port (4) and transports the predetermined flow of the gas mixture through the sensor array 1.

29. The apparatus according to claim 20, wherein a mixing ratio of the sample gas stream is calculated by the evaluation computer (20) and furnished as a display signal the evaluation computer (20).

30. The apparatus according to claim 20, wherein the evaluation computer (20) serves for continuously monitoring and regulating a mixing process.

31. The apparatus according to claim 20, wherein the evaluation computer (20) optically images a characterizing diagram of a gas compound.

32. The apparatus according to claim 20, wherein the evaluation computer (20) optically images and stores a sample pattern of a gas mixture.

33. The apparatus according to claim 20 further comprising a reversible feed transport pump (10) for filling the selective collection unit (7) by the suction power of the reversible feed transport pump (10) and for emptying again the selective collection unit (7) based on the pressure power of the reversible feed transport pump (10).