Detection Principle - Emerson Rosemount 625IR Manual

Description and detection principle
January 2024
A.1

Detection principle

The Rosemount 625IR uses an optical detection principle. The basic working principle is
illustrated in
Figure A-2: 625IR detection principle
A. Light source: Generates infrared light (2-6 μm region) and directs it to B.
B. Sapphire lens: Focuses light so that it passes through C.
C. Gas to be measured: The gas will absorb some wavelengths, depending on the type of
D. Mirror: After passing through the gas, the remaining light is reflected by a mirror back
E. Light sensors: Measure what wavelengths have been absorbed and how much light has
In addition to the basic principles described in
to compensate for changes, such as temperature and component aging over time.
58
Figure A-2 and consists of the following basic parts:
gas. The higher the concentration of the gas, the more light is absorbed.
through the gas again, reaching the lens directly at E.
been absorbed. Based on this information, the gas detector can decide if the target gas is
above the alarm level.
MS-00809-0100-3625
Figure A-2, the detector has more functions
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