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2.3.1 TDLAS Control Module and Laser Source
The TDLAS Control Module is an electronics board mounted inside the Optics / Sample Cell
enclosure. The laser source is mounted on this electronics board and connected to the sample cell
laser launcher optics via a telecommunications grade optical fibre. The TDLAS Control Module
with Laser source is shown in Figure 8.
Figure 5: TDLAS Control Module and Laser Source
The laser source is mounted just to the right of the centre of the board in the photo, along with
its associated heating and cooling equipment used for the tuning of the output wavelength.
2.3.4 Cell Heater
The sample cell and associated optical components are heated to 40°C to ensure measurement
stability. The block heater is visible just to the left of the TDLAS control module in Figure 11. The
temperature is controlled precisely by a PID heater controller on the analyzer’s IO Board. The cell
temperature is monitored using an RTD that sends signals back to the IO board, and this
2.3.5 Vacuum Pump
To improve the separation between the chosen absorbance wavelength for the target gas and
absorbance wavelengths of other interfering species, the interior of the sample cell is maintained
at a partial vacuum by use of a vacuum pump. The vacuum pump of the AccuLase-GPA™ is shown
in Figure 12. The vacuum pump is an oil-free design with very low maintenance requirements. It
is also mounted to the same metal frame as all the other components in the optics / sample cell
enclosure. The cell pressure is monitored using a pressure transducer that sends signals to the
analyzer’s IO board, and this pressure is available for display on both the analyzer’s local display
screen and in the web-based GUI software.
2.4 Sample Conditioning System
The sample conditioning system is used to ensure that the conditions of the sample entering the sample
cell are within the required specifications. A typical sample conditioning system for an AccuLase-GPA™.
A typical sample conditioning system for the AccuLase-GPA™ will include switching valves, a pressure
regulator, a liquid membrane separator, and a sample sweep valve.
