Gas Filter Correlation; Figure 10-1: Measurement Fundamentals; Figure 10-2: Gfc Wheel - Teledyne 300E Instruction Manual

Model 300E Carbon Monoxide Analyzer
Instruction Manual
IR
Source
Upon exiting the sample cell, the beam shines through a band-pass filter that
allows only light at a wavelength of 4.7µm to pass. Finally, the beam strikes a
solid-state photo-detector that converts the light signal into a modulated voltage
signal representing the attenuated intensity of the beam.

10.1.3. Gas Filter Correlation

Unfortunately, several gases also absorb light at 4.7µm. Among these are water
and carbon dioxide, both of which are much more common gases, compared to CO.
To overcome the interfering effects of these, as well as other, gases the Model 300E
adds another component to the IR Light path called a Gas Filter Correlation (GFC)
Wheel (see Figure 10-2).
P/N 04288 Rev: A
Sample Chamber
IR Beam

Figure 10-1: Measurement Fundamentals

Figure 10-2: GFC Wheel

Band-Pass
Measurement
Cell
(Pure N )
2
Reference Cell
(N with CO)
2
THEORY OF OPERATION
Filter
Photo-Detector
157