ABB AO2000-LS25 Laser analyzers

ABB AO2000-LS25 Laser analyzers

The analyzer is an optical instrument for continuous in-situ gas monitoring in stack, pipes,

process chambers or similar and is based on tunable diode laser absorption spectroscopy

(TDLAS). The analyzer utilizes a transmitter/receiver configuration (mounted diametrically

opposite each other) to measure the average gas concentration along the line-of-sight path.

The measuring principle is infrared single-line absorption spectroscopy, which is based on

the fact that each gas has distinct absorption lines at specific wavelengths. The measuring

principle is illustrated in Figure 1-1. The laser wavelength is scanned across a chosen absorption

line of the gas to be measured. The absorption line is carefully selected to avoid cross

interference from other (background) gases. The detected light intensity varies as a function

of the laser wavelength due to absorption of the targeted gas molecules in the optical path

between transmitter and receiver. In order to increase sensitivity the wavelength modulation

technique is employed: the laser wavelength is slightly modulated while scanning the absorption

line. The detector signal is spectrally decomposed into frequency components at harmonics

of the laser modulation frequency. The second harmonics of the signal is used to

measure the concentration of the absorbing gas. The line amplitude and line width are both

extracted from the second harmonics line shape, which makes the measured concentration

insensitive to line shape variations (line broadening effect) caused by background gases.

Software start-up

After starting the program a welcome screen will display a selection of instrument to PC connections:

The version of the service program is printed in the right bottom corner (in the example

above V.1.2.5.1).

For direct serial or modem connection, select the PC serial port from the dropdown list of

available ports and press the corresponding button. When using a modem, you will be asked

for a telephone number to dial. If the first digit in this phone number is zero, the software will