SS500XP/SS2000XP Gas Analyzer
BA02183C
1
–
6
Hauser
Figure 1–2 shows the typical raw data (in arbitrary units [a.u.]) from a laser
absorption spectrometer scan including the incident laser intensity,
I
0
(
)
,
and
the transmitted intensity,
I
(
), for a clean system and one with contaminated
mirrors (shown to illustrate the system’s relative insensitivity to mirror
contamination). The positive slope of raw data results from ramping the current
to tune the laser, which not only increases the wavelength with current, but
also causes the corresponding output power to increase. By normalizing the
signal by the incident intensity, any laser output fluctuations are canceled, and
a typical, yet more pronounced, absorption profile results. Refer to Figure 1–3.
3.0
2.5
2.0
1.5
1.0
0.5
Incident Energy
I
0
(
)
Raw Signal,
I
(
)
Raw Signal,
I
(
)
(Contaminated Mirrors)
Wavelength [a.u.]
S
ig
na
l [
a.
u.
]
0.0
Figure 1–2
Typical raw signal from a laser diode
absorption spectrometer with and without mirror
contamination
1.0
0.99
0.98
0.97
0.96
0.95
Normalized Absorption Signal
Wavelength [a.u.]
S
ig
na
l [
a.
u.
]
Figure 1–3
Typical normalized absorption signal
from a laser diode absorption spectrometer
