GLA531 Series LGR-ICOS™ Gas Analyzer
Operating Manual
3KXG165002R4201_2021_04
ABB PROPRIETARY INFORMATION 18
S = absorption line strength of the probed transition
L = optical path length of the laser beam through the sample
X = mole fraction
P = gas pressure
Φ
v
= line-shape function of the transition at frequency v
In this case:
Equation 2
∫
(
)
=
If the laser line width is much narrower than the width of the absorption feature, high-resolution absorption
spectra may be recorded by tuning the laser wavelength over the probed feature.
Integration of the measured spectra with the measured values of:
• Gas temperature
• Gas pressure
• Path length
• Line strength of the probed transition
allows calculations to determine the mole fraction directly from the relation:
Equation 3 =
∫
This equation determines gas concentrations, even in hostile environments, without using calibration gases or
reference standards.
The values measured are:
• Mixtures containing several species
• Flows at elevated temperatures and pressures
Figure 11 Typical Laser Absorption Spectroscopy Setup
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