Campbell Scientific TGA100 Trace Gas Analyzer Manual - Manual (Page 95)

8.2 Lasers
The TGA100 uses a lead-salt tunable diode laser. These lasers are available from 1000 to 3250 cm -1 . Each gas species
has a unique set of absorption lines, and tunable diode lasers have limited tuning ranges. Therefore, in most cases a
different laser is required for each gas species to be measured. The laser dewar can accommodate one or two lasers,
allowing the user to select a different gas without opening the dewar to install a different laser. The most commonly
used lasers are listed in
. This table also lists the frequencies for the preferred absorption lines. Contact
Campbell Scientific for other laser options.
Table 13
Table 13. Laser Part Numbers and Preferred Frequencies for Selected Trace Gases
CSI PN Gas Name Preferred
Frequencies (cm -1 )
7990 Nitrous Oxide (N
2
O) 2205.691
2208.575
2211.398
2233.273
2240.439
7992 Methane (CH
4
) 3017.467
3017.711
3018.529
3095.179
17467 Carbon Dioxide δ 13 C 2293.7 to 2294.6
17468 Carbon Dioxide
δ 13 C or δ 18 O
2308.1 to 2308.5
2310.1 to 2310.8
2311.3 to 2312.1
The TGA100 includes a dewar cable for a single laser in position one. A position 2 laser cable (CSI PN 8098) is
required if a second laser is installed in position two.
8.3 TGAHEAT Temperature Controller
The TGA100 temperature controller is recommended when the TGA100 is operated in the field without a shelter. It
heats the TGA100 enclosure to prevent condensation and maintains a more consistent temperature to reduce the errors
associated with diurnal temperature changes. The TGA100 temperature controller has two independently controlled 60
W heaters that are factory-installed in the TGA100 enclosure.
To operate the temperature controller, adjust the temperature setting with a small screwdriver. The temperature
adjustment is in the center of the temperature controller module, mounted in the electronics chassis in the analyzer
enclosure. The temperature should be set to 5 to 10 ºC above the maximum dew point temperature expected, to prevent
condensation on the window of the laser dewar.
Plug the temperature controller into AC power (85 to 264 Vac, 47 to 63 Hz, 185 W).
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