SS2100 TDLAS H
2
S Gas Analyzer BA02191C
1-6 Endress+Hauser
Figure 1–2 shows the typical raw data (in arbitrary units [u.a.]) 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 intensity 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
on page 1–7.
Note that contamination of the mirrors results solely in lower overall signal.
However, by tuning the laser off-resonance as well as on-resonance and
normalizing the data, the technique self calibrates every scan resulting in
measurements that are unaffected by mirror contamination.
OPTICAL HEAD
DETECTOR
WINDOW
OUTLET
TEC
LASER
INLET
PRESSURE
SENSOR
FAR MIRROR
Figure 1–1 Schematic of a
typical laser diode absorption
spectrometer
To Next Page
Loading...
Need help?
General
