Nondispersive infrared gas analyzer

• US 4,281,248 A
• Filed: 04/30/1980
• Issued: 07/28/1981
• Est. Priority Date: 05/05/1979
• Status: Expired due to Term

• Current Assignee: Hartmann & Braun AG (ABB Limited)
• Original Assignee: Hartmann & Braun AG (ABB Limited)
• Inventors: Fabinski, Walter, Deptolla, Udo
• Primary Examiner(s): Willis, Davis L.
• Application Number:
  US06/145,364
• Time in Patent Office: 454 Days
• Field of Search: 250/343, 250/345, 250/346, 356/51, 356/306, 356/437
• US Class Current: 250/345
• CPC Class Codes: G01N 21/37 using pneumatic detection opto-acoustic detection G01N21/1702
• CPC Class Codes: G01N 21/61 Non-dispersive gas analysers G01N21/3504 takes precedence

Abstract

The cross-sensitivity of a two-beam infrared gas analyzer is reduced by using two differently long cells for the sample gas in the two beam paths. The path with the short sample gas cell is intercepted by a detector cell having highly absorbing wall while the detector cell in the other path is highly reflective, e.g., made of gold. The two detector cells are interconnected by a differential pressure chamber with capacitive pickup.

Claims

1. A nondispersive infrared gas analyzer having a source for infrared radiation as well as means for defining a first and a second path as well as chopper means for periodically interrupting radiation in each of said paths, further including first and second detection cells filled with gas of the type to be detected in the sample gas, the cells being respectively disposed in said first and second paths, there being additionally differential pressure sensing means with capacitive pickup connected to the first and second detection cells for responding to pressure differences in those detection cells and providing an electrical signal representative thereof, the improvement comprising:

a first and a second cell for sample gas, respectively disposed in the first and the second path, the first cell being significantly shorter in the direction of the first path than the second cell; and

the walls of the first detection cell absorbing more radiation than the walls of the second detection cells.

2. An analyzer as in claim 1, the walls of the first detection cell being black, the walls of the second detection cell being reflective.

3. An analyzer as in claim 1 or 2, the walls of the second detection cell being made of gold.

4. An analyzer as in claim 1 or 2, the first cell including additional absorbing means having a low heat capacity.

5. An analyzer as in claim 4, the additional means being a blackened wire mesh.