Teledyne LGA-3500 - Laser Gas Analysis system - Manual (Page 23)

Laser Gas Analyzer Operational Theory
Teledyne Analytical Instruments 9
to their vulnerability to interference from background gases and dust,
cannot or can hardly conduct on-the-spot measurement.
Figure 2.2 Schematic of “Single line” Spectroscopy.
The Model 3500 series of analyzers do not need complex gas
sampling and pretreatment. They have extremely quick response
because they skip the long gas sampling and transport process. As a
result, system maintenance is minimal since gas sampling and
pretreatment systems contribute to the majority of the maintenance
workload for conventional sampling gas analysis systems.
In conventional sampling gas analysis systems, it is the gas
concentration in the vicinity of the sampling tip that is sampled and
measured. Since gas concentration can have significant variance across
the section of gas flow pipe, inaccurate measurements result. No matter
how precise the subsequent data analysis is, the measurement results do
not accurately indicate the overall gas concentration in the gas flow pipe.
In contrast, the Model 3500 measures the average gas concentration
from the transmitter to the receiver. This represents the gas
concentration of the gas flow process much more accurately.
In addition, laser gas analysis systems have built-in temperature
and pressure auto-correction capability to enhance measurement
accuracy. These systems compensate for the temperature and pressure