User's Manual

2-2
where
– intensity of light before pass through the gas
volume;
– intensities of light after pass through the gas
volume;
– absorption coefficient of the gas at the chosen
light wavelength;
– optical pass length;
– gas concentration.
At a fixed and
known
absorption it is
possible to find
gas concen-
tration using
measured
intensity of light
(measuring
channel) that
passed from
Light Emitter to
Photodetector.
I
I
L
X
L
0
a
a
According to the Beer-Bouguer-Lambert law, light
absorption in a gas volume is proportional to the
absorbing gas concentration:
e
XL
I
I
0
a-
×
=
REV. 1.10/2002
RMT LtdRMT Ltd
RMT LtdRMT Ltd
DX6106
4.0
Fig. 2.2. Spectral bands of light
emitters for methane analyzer
2.0
0
0.5
1.0
3.0
Reference
channel
Photodetector
Measuring
channel
Relative response
Wavelength, mµ