METHOD AND DEVICE FOR ESTIMATING A GASEOUS COMPONENT

• US 3,849,005 A
• Filed: 04/13/1973
• Issued: 11/19/1974
• Est. Priority Date: 04/21/1972
• Status: Expired due to Term

• Current Assignee: Andre Girard, Jean Laurent
• Original Assignee: Andre Girard, Jean Laurent
• Inventors: Girard, Andre, Laurent, Jean
• Primary Examiner(s): McGraw, Vincent P.
• Application Number:
  US05/350,975
• Time in Patent Office: 585 Days
• Field of Search: 356/51,201 250/338,345,353
• US Class Current: 356/438
• CPC Class Codes: G01N 21/3518 Devices using gas filter correlation techniques; Devices using gas pressure modulation techniques

Abstract

The absorption or emission of a characteristic radiation of the component is measured. The device comprises two chambers containing a predetermined weight of the component to be estimated. The second chamber contains a weight of this component greater than that in the first chamber. A third chamber contains no absorbing component. A beam of radiation coming from the mixture to be analysed passes alternately through the first two chambers, then half through each of the two other chambers. A detector receives the beam coming from the chambers through a filter. The method and device are useful for the estimation of pollutants in the atmosphere.

Claims

1. Method for determining a component of interest of a gaseous mixture, said method using the absorption or the emission of a characteristic radiation of said component and comprising alternately and cyclically passing a beam of radiation emerging from said mixture and whose spectral composition contains at least one characteristic ray of the component through an enclosure through which the beam encounters a predetermined weight of the component of interest and splitting said beam and simultaneously passing part of said beam through a second enclosure where the beam encounters a weight of the component of interest greater than said predetermined weight and the remainder of said beam through a weight of said component substantially less than said predetermined weight, and measuring the cyclical variations in the beam which alternately is passed through said first enclosure and is passed partly through said second enclosure and partly through said lesser weight of component.

2. Method according to claim 1, wherein one half of the beam is passed through the second of said enclosures and the other half of said beam is passed through a weight substantially nil of said component.

3. Method according to claim 1, wherein said predetermined weight is selected so that the variations in intensity are nil when the said gaseous mixture does not contain said component.

4. Device for determining a component of interest of a gaseous mixture using absorption or emission by said mixture of a characteristic radiation of the component, said device comprising a first enclosure containing a predetermined weight of the component of interest, a second enclosure containing a weight of the component of interest greater than said predetermined weight and a third enclosure containing a weight substantially nil of said component of interest, means for receiving a beam of radiation emerging from said mixture, and alternately and cyclically first directing the whole of said beam through the first enclosure, and then directing a predetermined part of said beam through the second enclosure and the remainder of said beam through the third enclosure, a filter located on the paths of said beam from the enclosures and transparent for part only of the spectral absorption or emission band of said component, a detector positioned to receive the beam transmitted by the filter, and means for measuring the variations in the output signal from the detector.

5. Device according to claim 4, wherein the first enclosure is constituted by a group of two chambers offering the beam each a predetermined passage cross-area, and the second and third enclosures being constituted by chambers having the same length and the same cross-area as each of said two chambers.

6. Device according to calim 4, wherein the first, second and third enclosures consist of first, second and third chambers, respectively, the first chamber offering the beam a cross-area double the cross-area of each of the two other chambers.

7. Device according to claim 4, wherein the detector and the filter are cooled to a cryogenic temperature.

8. Device according to claim 6, wherein the chambers each contain a gas which does not absorb in the band width of the filters, the first and the second chambers containing in addition predetermined contents of said component, the partial pressure of said component in the fiRst chamber being greater than its partial pressure in the second chamber.

9. Device according to claim 4, comprising a concentrating optical device located in the beam before said directing means and providing, from a cylindrical input beam, a cylindrical output beam of smaller diameter having a constant energy density if the input beam has a constant energy density.

10. Device according to claim 4, wherein the weights of the constituent of interest in said enclosures are such that the output signal is nill when said mixture contains a nil content of said constituent.

11. Device according to claim 9, wherein said concentrating optical device is a telescope.