Figure 7-3: Measurement Fundamentals With Gfc Wheel - Teledyne T360 Operation Manual

Teledyne API Model T360/T360M Operation Manual
7.1.3.1. THE GFC WHEEL
IR unaffected by N in Measurement Cell
2
IR IS affected by CO
IR
Source
GFC Wheel
Figure 7-3:
07272B DCN6552
A GFC wheel is a metallic wheel into which two chambers are carved. The
chambers are sealed on both sides with material transparent to 4.3 µm IR
radiation creating two airtight cavities.
composed gases. One cell is filled with pure N
filled with a combination of N
cell).
in Reference Cell
2
M
R
Measurement Fundamentals with GFC Wheel
As the GFC wheel spins, the IR light alternately passes through the two cavities.
When the beam is exposed to the reference cell, the CO
strips the beam of most of the IR at 4.3μm. When the light beam is exposed to
the measurement cell, the N
results in a fluctuation in the intensity of the IR light striking the photo-detector
(Figure 7-3) that results in the output of the detector resembling a square wave
such as that shown in Figure 7-4.
Each cavity is filled with specially
(the measure cell)
2
and a high concentration of CO
2
in the filter wheel does not absorb IR light. This
2
Principles of Operation
The other is
.
(the reference
2
Δ H
Photo-Detector
in the gas filter wheel
2
195