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1
I
NTRODUCTION
748250-L Rosemount Analytical October 1999
1-1
Model 880A Non-Dispersive Infrared Analyzer
1.1 GENERAL DESCRIPTION
The Model 880A Non-Dispersive Infrared Analyzer is designed to continuously
determine the concentration of a particular component of interest in a flowing gaseous
mixture. Within the analyzer, two equal energy infrared beams are directed through
two parallel optical cells, a flow-through sample cell and a reference cell. The Luft
detector continuously measures the difference in the amount of infrared energy
absorbed within each of the two cells. This difference is a measure of the
concentration of the component of interest in the sample.
Readout is on the 16-character, backlighted liquid crystal display in parts per million,
percent of composition or percent of fullscale. Additionally, a 0 to +5 VDC output for a
potentiometric (voltage) recorder is provided as standard.
A linearizer, based on a fourth-order polynomial, is incorporated in the electronic
circuitry. By turning the linearizer ON and entering the correct coefficients, an output
linear with concentration is obtained.
F
IGURE
1-1. M
ODEL
880A D
ETECTION
S
YSTEM
INFRARED
SOURCE
DETECTOR
SIGNAL
SIGNAL
CONDITIONING
CIRCUITRY
REFERENCE
CELL
STATIONARY
BUTTON
CHOPPER
SAMPLE IN
SAMPLE
CELL
SAMPLE OUT
DIAPHRAGM
DISTENDED
COMPONENT OF INTEREST
OTHER MOLECULES
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