Gas sensor with phased heaters for increased sensitivity

• US 6,393,894 B1
• Filed: 07/27/1999
• Issued: 05/28/2002
• Est. Priority Date: 07/27/1999
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell International Inc.
• Inventors: Bonne, Ulrich, Dasgupta, Purnendu K., Goetz, Jay
• Primary Examiner(s): LARKIN, DANIEL SEAN
• Application Number:
  US09/361,886
• Time in Patent Office: 1,036 Days
• Field of Search: 73/23.2,31.07 422/88
• US Class Current: 73/23.2
• CPC Class Codes: G01N 1/2214 by sorption
• CPC Class Codes: G01N 1/40 Concentrating samples
• CPC Class Codes: G01N 1/405 by adsorption or absorption
• CPC Class Codes: G01N 2030/123 using more than one trap
• CPC Class Codes: G01N 2030/3015 temperature gradients along column
• CPC Class Codes: G01N 2030/3076 using specially adapted T(t) profile
• CPC Class Codes: G01N 30/12 by evaporation

Abstract

A concentrator and sensor assembly are disclosed that use phased heaters to multiply the concentration levels that can be eluted, relative to operation with a single interactive element having a sorbent material to increase the concentration of desired gas constituents at a detector. This is accomplished here by providing two or more interactive concentrator elements that are selectively heated in a time phased sequence so that each of the interactive elements becomes heated and desorbs gas constituents into the sample fluid stream at substantially the same time that an upstream concentration pulse, produced by heating one or more upstream interactive elements, reaches the interactive element. This produces a multiplication effect that significantly increases the concentration of the gas constituents at the detector, thereby increasing the effective sensitivity of the detector.

Claims

1. A concentrator for concentrating one or more constituents of a sample fluid stream, comprising:

two or more interactive elements spaced along and exposed to the sample fluid stream, each of the interactive elements include an interactive substance that adsorbs and desorbs selected constituents of the sample fluid stream depending on the temperature of the interactive element, wherein at least two of the interactive elements include the same interactive substance;

two or more heater elements, each heater element in thermal communication with a corresponding interactive element; and

controller means coupled to the two or more heater elements for allowing the two or more interactive elements to become exposed to the sample fluid stream before energizing the heater elements in a time phased sequence.

2. A concentrator according to claim 1, wherein the two or more interactive elements comprise different portions of an interactive layer exposed to and extending along at least part of the sample fluid stream.

3. A concentrator according to claim 2, wherein each of the two or more heater elements are in thermal communication with a corresponding portion of the interactive layer.

4. A concentrator according to claim 1, wherein the interactive elements are of equal length.

5. A concentrator according to claim 1, wherein the interactive substance is a silica gel.

6. A concentrator according to claim 1, wherein the interactive substance is an active carbon.

7. A concentrator for concentrating one or more constituents of a sample fluid stream, comprising:

two or more interactive elements spaced along and exposed to the sample fluid stream, each of the interactive elements include an interactive substance that adsorbs and desorbs selected constituents of the sample fluid stream depending on the temperature of the interactive element;

two or more heater elements, each heater element in thermal communication with a corresponding interactive element; and

controller means coupled to the two or more heater elements for allowing the two or more interactive elements to become exposed to the sample fluid stream before energizing the heater elements in a time phased sequence, said controller means including first energizing means for energizing a first heater element, second energizing means for energizing a second heater element that is located downstream of the first heater element, and a controller for activating said first energizing means, which causes the corresponding interactive element to become heated and desorb selected constituents into the sample fluid stream which produces a first concentration pulse that is carried by the sample fluid stream downstream toward the second heater element, and for activating said second energizing means when the first concentration pulse reaches the second heater element.

8. A concentrator according to claim 7, wherein the first heater element and the second heater element include a resistive material.

9. A concentrator according to claim 8, wherein said first energizing means energizes said first heater clement by providing a first voltage, currents, or power pulse, and said second energizing means energizes said second heater element by providing a second voltage, current, or power pulse.

10. A concentrator for concentrating one or more constituents of a sample fluid stream, comprising:

two or more interactive elements spaced along and exposed to the sample fluid stream, each of the interactive elements include an interactive substance that adsorbs and desorbs selected constituents of the sample fluid stream depending on the temperature of the interactive element;

two or more heater elements, each heater element in thermal communication with a corresponding interactive element; and

controller means coupled to the two or more heater elements for energizing the heater elements in a time phased sequence, said controller means including first energizing means for energizing a first heater element with a first energy pulse, second energizing means for energizing a second heater element that is located downstream of the first heater element with a second energy pulse, and a controller for activating said first energizing means, which causes the corresponding interactive element to become heated and desorb selected constituents into the sample fluid stream which produces a first concentration pulse that is carried by the sample fluid stream downstream toward the second heater element, and for activating said second energizing means when the first concentration pulse reaches the second heater element, wherein the first energy pulse and the second energy pulse result in triangular shaped temperature pulses of the adsorption layer.

11. A concentrator for concentrating one or more constituents of a sample fluid stream, comprising:

two or more interactive elements spaced along and exposed to the sample fluid stream, each of the interactive elements include an interactive substance that adsorbs and desorbs selected constituents of the sample fluid stream depending on the temperature of the interactive element;

two or more heater elements, each heater element in thermal communication with a corresponding interactive element; and

controller means coupled to the two or more heater elements for energizing the heater elements in a time phased sequence, said controller means including first energizing means for energizing a first heater element with a first energy pulse, second energizing means for energizing a second heater element that is located downstream of the first heater element with a second energy pulse, and a controller for activating said first energizing means, which causes the corresponding interactive element to become heated and desorb selected constituents into the sample fluid stream which produces a first concentration pulse that is carried by the sample fluid stream downstream toward the second heater element, and for activating said second energizing means when the first concentration pulse reaches the second heater element, wherein the first energy pulse and the second energy pulse result in square shape temperature pulses of the adsorption layer.

12. A concentrator for concentrating one or more constituents of a sample fluid stream, comprising:

two or more interactive elements spaced along and exposed to the sample fluid stream, each of the interactive elements include an interactive substance that adsorbs and desorbs selected constituents of the sample fluid stream depending on the temperature of the interactive element;

two or more heater elements, each heater element in thermal communication with a corresponding interactive element; and

controller means coupled to the two or more heater elements for energizing the heater elements in a time phased sequence, said controller means including first energizing means for energizing a first heater element with a first energy pulse, second energizing means for energizing a second heater element that is located downstream of the first heater element with a second energy pulse, and a controller for activating said first energizing means, which causes the corresponding interactive element to become heated and desorb selected constituents into the sample fluid stream which produces a first concentration pulse that is carried by the sample fluid stream downstream toward the second heater element, and for activating said second energizing means when the first concentration pulse reaches the second heater element, wherein the first energy pulse and the second energy pulse result in bell shaped temperature pulses of the adsorption layer.

13. A concentrator for concentrating one or more constituents of a sample fluid stream, comprising:

two or more interactive elements spaced along and exposed to the sample fluid stream, wherein each of the interactive elements includes an interactive substance that adsorbs and desorbs selected constituents of the sample fluid stream depending on the temperature of the interactive element wherein each of the interactive elements has a length that is greater than the length of each interactive clement located further upstream in the sample fluid stream;

two or more heater elements, each heater element in thermal communication with a corresponding interactive element; and

controller means coupled to the two or more heater elements for energizing the heater elements in a time phased sequence.

14. A sensor assembly for sensing the enhanced concentration of one or more constituents in a sample fluid stream, comprising:

two or more interactive elements spaced along and exposed to the sample fluid stream, each of the interactive elements include an interactive substance that adsorbs and desorbs selected constituents of the sample fluid stream depending on the temperature of the interactive element;

two or more heater elements, each heater element in thermal communication with a corresponding interactive element;

controller means coupled to the two or more heater elements for allowing the two or more interactive elements to become exposed to the sample fluid stream before energizing the heater elements in a time phased sequence such that each of the interactive elements becomes heated and desorbs selected constituents into the sample fluid stream at substantially the time that an upstream concentration pulse, produced by one or more upstream interactive elements, reaches the interactive element;

separator means for separating selected constituents of one of the concentration pulses provided by one or more of the interactive elements into individual constituent components; and

detector means for sensing the concentration of one or more of the individual constituent components.

15. A sensor assembly according to claim 14, wherein said detector means includes a thermal conductivity detector.

16. A sensor assembly according to claim 14, further comprising a pump for providing the sample fluid stream.

17. A sensor assembly according to claim 14, wherein the sample fluid stream is driven by thermal convection.

18. A sensor assembly according to claim 14, further includes a preheater for preheating at least a portion of the sample fluid stream.

19. A sensor assembly according to claim 18, wherein said preheater heats the sample fluid stream throughout the sensor assembly.

20. A sensor assembly according to claim 18, wherein said preheater heats the sample fluid stream only in the separation means.

21. A sensor assembly according to claim 14, further includes a cooler for cooling at least a portion of the sample fluid stream.

22. A method for concentrating one or more constituents of a sample fluid stream, the method comprising the steps of:

providing two or more interactive elements spaced along and exposed to the sample fluid stream, each of the interactive elements include an interactive substance that adsorbs and desorbs selected constituents of the sample fluid stream depending on the temperature of the interactive clement, where at least two of the interactive elements include the same interactive substance;

waiting for the interactive substance to adsorb one or more constituents from the sample fluid stream; and

heating the two or more interactive elements in a time phased sequence.

23. A method for concentrating one or more constituents of a sample fluid stream, the method comprising the steps of:

providing two or more interactive elements spaced along and exposed to the sample fluid stream, each of the interactive elements include an interactive substance that adsorbs and desorbs selected constituents of the sample fluid stream depending on the temperature of the interactive element, where at least two of the interactive elements incorporate the same interactive substance;

waiting for the interactive substance to adsorb one or more constituents from the sample fluid stream; and

heating the two or more interactive elements in a time phased sequence, wherein said heating step includes the steps of;

heating an upstream interactive element, which causes the upstream interactive element to desorb selected constituents into the sample fluid stream to produce a first concentration pulse that is carried by the sample fluid stream downstream toward a downstream interactive element; and

heating the downstream interactive element when the first concentration pulse reaches the downstream interactive element, which causes the downstream interactive element to desorb selected constituents into the sample fluid stream and at least partially overlap the first concentration pulse to produce a second concentration pulse that is carried by the sample fluid stream downstream.

24. A method for concentrating one or more constituents of a sample fluid stream, the method comprising the steps of:

providing N interactive elements, where N is greater than one, each of the N interactive elements being spaced along and exposed to the sample fluid stream, each of the N interactive elements including an interactive substance that adsorbs and desorbs selected constituents of the sample fluid stream depending on the temperature of the interactive element such that, when heated, each of the N interactive elements desorb selected constituents into the sample fluid stream to produce a corresponding concentration pulse that is carried by the sample fluid stream downstream toward a downstream interactive element;

exposing the N interactive elements to the sample fluid stream;

waiting for the N interactive elements to adsorb one or more constituents from the sample fluid stream; and

heating the N interactive elements in a time phased sequence whereby each of the downstream interactive elements is heated when the concentration pulse provided by one or more of the upstream interactive elements reaches the downstream interactive element.

25. A method according to claim 24, further comprising the step of sensing the concentration of selected constituents present in the concentration pulse provided by one or more of the N interactive elements.

26. A method according to claim 25, further comprising the step of separating selected constituents of the concentration pulse provided by one or more of the N interactive elements into individual components.

27. A method according to claim 26, further comprising the step of sensing the concentration of one or more of the individual components.

28. A method for concentrating one or more constituents of a sample fluid stream that is flowing through a channel having an interactive substance provided therein, the interactive substance adsorbing and desorbing selected constituents of the sample fluid stream depending on the temperature of the interactive substance, the interactive substance having an upstream portion and a downstream portion, the method comprising the steps of:

waiting for the interactive substance to adsorb one or more constituents from the sample fluid stream;

heating the upstream portion of the interactive substance, causing the upstream portion to desorb selected constituents into the sample fluid stream to produce a first concentration pulse, the first concentration pulse is carried by the sample fluid stream downstream toward the downstream portion of the interactive substance; and

heating the downstream portion of the interactive substance when the first concentration pulse reaches the downstream portion, causing the downstream portion of the interactive substance to desorb selected constituents into the sample fluid stream and at least partially overlap the first concentration pulse to produce a second concentration pulse that is carried by the sample fluid stream downstream.

29. A concentrator for concentrating one or more constituents of a sample fluid stream, comprising:

two or more interactive elements spaced along and exposed to the sample fluid stream, each of the interactive elements include an interactive substance that adsorbs and desorbs selected constituents of the sample fluid stream depending on the temperature of the interactive element, wherein at least two of the interactive elements are disposed within the sample fluid stream such that the sample fluid must pass by a first interactive element and then a second interactive element;

two or more heater elements, each heater element in thermal communication with a corresponding interactive e element; and

controller means coupled to the two or more heater elements for allowing the two or more interactive elements to become exposed to the sample fluid stream before energizing the heater elements in a time phased sequence.