Gas sample chamber for use with a source of coherent radiation

• US 5,384,640 A
• Filed: 01/19/1993
• Issued: 01/24/1995
• Est. Priority Date: 01/19/1993
• Status: Expired due to Fees

• Current Assignee: GE Security Incorporated (Carrier Global Corporation)
• Original Assignee: Gaztech International Corporation
• Inventors: Wong, Jacob Y.
• Primary Examiner(s): Willis, Davis L.
• Assistant Examiner(s): KEESEE, LACHARLES
• Application Number:
  US08/005,759
• Time in Patent Office: 735 Days
• Field of Search: 356/437, 73/31.02, 250/343
• US Class Current: 356/437
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis
• CPC Class Codes: G01N 21/39 using tunable lasers

Abstract

A gas sample chamber that is particularly advantageous for use with a semiconductor laser has the form of an elongated hollow tube with a specularly reflective inside surface, a semiconductor laser located at one end of the tube and a detector located at the opposite end of the tube. In one embodiment, apertures in the wall of the tube permit a gas to enter and leave the sample chamber by free diffusion. In another embodiment the gas flows into the hollow tube from a pressurized source through a port or is drawn through the tube by a suction pump. In other embodiments, the tube is partitioned into two successive sections by means of a window located within the tube. The window is transparent to radiation of two different wavelengths that coincide with the absorption bands of two different gases. The semiconductor laser is tuned to these wavelengths successively so that two gas components can be detected and measured simultaneously.

Claims

1. A gas sample chamber for use with a source of coherent radiation, comprising in combination:

an elongated hollow tube having a first end and a second end and having an inside surface that is specularly reflective, and including means for permitting the gas sample to enter and leave the space within said elongated hollow tube;

a semiconductor laser located at the first end of said elongated hollow tube and oriented to project radiation toward the second end;

a detector located at the second end of said elongated hollow tube and occupying substantially the entire cross section of said elongated hollow tube.

2. The gas sample chamber of claim 1 wherein said means includes at least two spaced apertures.

3. The gas sample chamber of claim 2 wherein said at least two spaced apertures are each covered by a semipermeable membrane.

4. The gas sample chamber of claim 3 wherein said semipermeable membrane prevents particles larger than 0.1 micron from entering said elongated hollow tube while not interfering with diffusion of a gas into and out of said elongated hollow tube.

5. The gas sample chamber of claim 2 further comprising heating means for warming said elongated hollow tube to prevent condensation of gases or vapors on the inside surface of said elongated hollow tube.

6. A gas sample chamber for use with a source of coherent radiation, comprising in combination:

an elongated hollow tube having a first end and a second end and having an inside surface that is specularly reflective;

semiconductor laser means located at the first end of said elongated hollow tube, oriented to project radiation toward the second end, and producing radiation having a first wavelength λ

₁ and a second wavelength λ

₂ ;

a window located between the first end and the second end of said elongated hollow tube, forming a gastight seal with the inside surface of said elongated hollow tube so as to partition said elongated hollow tube into a first section and a second section isolated from said first section, said window substantially transparent to radiation of wavelengths λ

₁ and λ

₂ ;

first means for permitting a first gas to enter and leave the first section and second means for permitting a second gas to enter and leave the second section; and

,

a detector located at the second end of said elongated hollow tube and occupying substantially the entire cross section of said elongated hollow tube.

7. The gas sample chamber of claim 6 wherein said first means include at least two spaced ports.

8. The gas sample chamber of claim 6 wherein said second means include at least two spaced ports.

9. The gas sample chamber of claim 6 wherein said first means includes at least two spaced apertures.

10. The gas sample chamber of claim 9 wherein said at least two spaced apertures are each covered by a semipermeable membrane.

11. The gas sample chamber of claim 10 wherein said semipermeable membrane prevents particles larger than 0.1 micron from entering said elongated hollow tube while not interfering with diffusion of said first gas into and out of said elongated hollow tube.

12. The gas sample chamber of claim 6 wherein said second means include at least two spaced apertures.

13. The gas sample chamber of claim 12 wherein said at least two spaced apertures are each covered by a semipermeable membrane.

14. The gas sample chamber of claim 13 wherein said semipermeable membrane prevents particles larger than 0.1 micron from entering said elongated hollow tube while not interfering with diffusion of said second gas into and out of said elongated hollow tube.

15. The gas sample chamber of claim 6 further comprising heating means for warming said elongated hollow tube to prevent condensation of gases or vapors on the inside surface of said elongated hollow tube.