The detector signal is spectrally decomposed into harmonic frequency components of the laser modulation frequency.

The second harmonic of the signal is used to measure the concentration of the absorbed gas.

Both line amplitude and line width are Both line amplitude and line width are extracted from the second harmonic line shape.

Therefore the measured concentration is not sensitive to changes in the line shape (line amplitude and line width).

The measured concentration is not sensitive to line shape changes (line width and line width) caused by background gases.

Note: The analyser measures only the concentration of free molecules in a given gas and is therefore not 

sensitive to molecules bound to other molecules in complexes and molecules attached to or dissolved in particles and droplets.

Care should be taken when comparing results with those obtained by other measurement techniques.

The receiver unit contains a focusing lens, photodetector and receiver electronics in a coated aluminium case.

Both the transmitter and receiver have an environmental protection rating of IP66.

The standard optical window is pressure resistant up to 5 bar (absolute pressure).

The monitor is mounted by assembling the transmitter and receiver with the supplied

purge and calibration unit and mounting to a DN50 process flange (see Figure 3-1).

Optical alignment is both simple and reliable, and the purge device prevents dust

and other contaminants from being deposited on the optical window.