LASERGASTM
II Multipass Monitor
The
LaserGas II Multipass monitor is a high performance gas monitor specially
designed for measurement of very low gas concentrations. Based on the
well-proven tuneable diode laser (TDLAS) technology the instrument has a number
of unique features.
?Short response time (typically 5-10 sec)
?No cross interference from other gases
?Very low detection limits (ppb for most
gases)
?Offline gas analysis in controlled
environment
?Turn-key instrument
?Low cost of ownership
?Ethernet connection
The
consists of 5 modules, the transmitter, receiver, Multipass cell, beam
alignment chamber and power supply unit, which are all integrated on a wall
mounted panel for easy installation. The standard Multipass cell is made of
stainless steel. Special (e.g. heatable) versions of these cells are available
on request. Measurement readings are provided through standard 4-20 mA current
loops, a fibre-optic output or the optional Ethernet interface. The latter
enables communication via a local area network or the Internet.
Measuring
principle
Unlike conventional UV or IR spectrographic instruments,
LaserGas II Monitors employ the measurement principle known as 'single line
spectroscopy', which eliminates cross interference from other gases. A single
gas absorption line with no cross interference is chosen in the near IR
spectral range and scanned by a single-mode diode laser. The laser beam is
coupled into the measurement cell, a so-called Herriot cell, where it is
reflected multiple times between two spherical mirrors. Subsequently a detector
collects the transmitted light for further analysis and calculation of the gas
concentration. With the Multipass concept a long optical path length (and low
detection limit) can be achieved with a very compact instrument.
Installation
and operation
The LaserGas II MP Monitor is a turn-key instrument, delivered
with factory calibration and tuned to the specific application. No other
operations than connecting sample gas tubes and optional purge are required
during installation. To avoid fouling of optical parts in the Multipass cell
the cleanliness of the sample gas must be ensured.
Filtering the sample gas in an appropriate extractive system may be required
for some applications. The instrument contains no moving parts, thereby
limiting preventive maintenance to visual inspection. Calibration checks are
recommended every 6-12 months.
Main
applications
The LaserGas II MP is designed for the detection of very low
gases concentrations (down to ppb level).
The following are some of the typical applications:
?Trace measurement of contaminants (e.g. O2,
H2O) in pure gases
?Trace measurements of contaminants in
reactive gases
used in the semiconductor industry
? Measurement of contaminants in natural
gas
?Low ppm H2S measurement in
process gases
? ppm NO measurement for emission control
Table
of Gases
|
Gas
|
Detection
limit
|
Min. meas.
range
|
|
O2
|
1 mg/m3
|
0 - 100 mg/m3
|
|
H2O
|
0,003 mg/m3
|
0 - 0,3 mg/m3
*
|
|
H2S
|
0,3 mg/m3
|
0 - 30 mg/m3
|
|
CH4
|
0,02 mg/m3
|
0 - 2 mg/m3
|
|
CO
|
3 mg/m3
|
0 - 300 mg/m3
|
|
CO2
|
3 mg/m3
|
0 - 300 mg/m3
|
|
NO
|
1,5 mg/m3
|
0 - 150 mg/m3
|
|
N2O
|
0,5 mg/m3
|
0 - 50 mg/m3
|
|
NH3
|
0,015 mg/m3
|
0 - 1,5 mg/m3
|
|
HCl
|
0,005 mg/m3
|
0 - 0,5 mg/m3
|
|
HF
|
0,0015 mg/m3
|
0 - 0,15 mg/m3
|
|
HCN
|
0,03 mg/m3
|
0 - 3 mg/m3
|
Remark:
Detection limits are specified for gas temperature / pressure = 25?C / 1 bar abs. (* lowest detection limit for H2O may only be achievable with special
sealing of the cell). Other gases and ultra-low CO and CO2 (range
0-3 mg/m3) are available on request.