Measurement by concentration of a material within a structure

• US 6,630,833 B2
• Filed: 03/09/2001
• Issued: 10/07/2003
• Est. Priority Date: 07/26/1994
• Status: Expired due to Term

• Current Assignee: Phase Dynamics, Inc.
• Original Assignee: Phase Dynamics, Inc.
• Inventors: Scott, Bentley N.
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): Hamdan, Wasseem H.
• Application Number:
  US09/803,716
• Publication Number:
  US 20020005725A1
• Time in Patent Office: 942 Days
• Field of Search: 324/633, 324/637, 324/639, 324/640, 324/642, 324/643, 324/647, 324/682, 324/690, 324/754, 333/34, 333/246, 333/263
• US Class Current: 324/637
• CPC Class Codes: G01N 22/00 Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more G01N3/00 - G01N17/00, G01N24/00 take precedence
• CPC Class Codes: G01N 22/04 Investigating moisture content
• CPC Class Codes: G01R 1/06772 High frequency probes
• CPC Class Codes: G01R 29/0878 Sensors; antennas; probes; detectors wave guide measuring sections G01R1/24

Abstract

Systems, methods, and probe devices for electronic monitoring and characterization using absorbent media confined by a metallic mesh. The mesh allows a stream of liquid or gas to pass through the structure, so that the media will adsorb the material to which it is specific. This changes the permittivity of the media in which the electromagnetic field is propagating. This change in permittivity can be seen through the use of classical microwave methods such as phase shift, amplitude changes, frequency changes in a cavity or the frequency of an unbuffered oscillator. Some embodiments use a two cylinder structure, where an outer cylinder contains a material which selectively removes a chemical which may be in conflict with or would contaminate the sensing of the desired chemical. This outer cylinder does not play a part in the measurement because it is outside the metal shield which contains the measurement adsorbent, and is thus outside the electromagnetic field.

Claims

1. A system for detecting the presence of a desired chemical, said system comprising:

an RF oscillator, which includes

a gain element which has substantial gain at frequencies greater than 100 MHz;

a feedback path, coupling the output of said gain element to the input thereof, said feedback path including a tunable resonant circuit;

an electromagnetic propagation structure which is RF-coupled to said oscillator, said propagation structure comprising;

a first metallic mesh enclosing said conductor; and

a first adsorbent media contained between said central conductor and said metallic mesh, said first adsorbent media selectively adsorbing said desired chemical;

wherein electromagnetic wave propagation is electrically loaded by said desired chemical and

circuitry connected to monitor the frequency of said oscillator to ascertain changes in the concentration of said chemical.

2. The system of claim 1, wherein said first adsorbent media comprises aluminum oxide.

3. The system of claim 1, wherein said first adsorbent media comprises Selexsorb.

4. The system of claim 1, wherein said first adsorbent media comprises Amberlite.

5. The system of claim 1, wherein said first adsorbent media comprises a polymeric adsorbent which can be used to remove organic pollutants from aqueous streams.

6. The system of claim 1, wherein said first adsorbent media comprises first and second adsorbent materials which are both selective to a given chemical, wherein said first adsorbent material has a stronger attraction for said given chemical than does said second adsorbent material.

7. The system of claim 1, further comprising a second adsorbent media through which a sampled stream must pass prior to reaching said first adsorbent media, said second adsorbent media adsorbing a chemical which can interfere with the detection of said desired substance.

8. A method for detecting a chemical in a fluid stream, said method comprising:

passing said fluid steam through a filter structure which adsorbs a second chemical which can interfere with the adsorption of said chemical;

passing at least part of the fluid stream through a mesh-confined propagation structure, said propagation structure adsorbing a concentration of said chemical which is at least ten times greater than the concentration of said chemical in said fluid stream;

using radio frequency waves to detect changes in said concentration of said chemical within said propagation structure.

9. The method of claim 8, wherein said propagation structure adsorbs a concentration of said chemical which is at least one hundred times greater than the concentration of said chemical in said fluid stream.

10. The method of claim 8, wherein said chemical is CO₂.

11. The method of claim 8, wherein said chemical is an organic material.