LaserGasTM II Multipass Monitor
The extractive Multipass monitor
allows a gas sample to be removed from the process and analysed offline. Based
on multiple reflections in the analysis cell, this instrument combines 11 m
measurement path with a very compact design and is designed for trace
measurements of for example H2O, O2 or H2S (see Table of
Gases below). Based on the well-proven tuneable diode laser (TDLAS)
technology the instrument has a number of unique features.
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 (optional)
The monitor 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 this cell are available on request. Measurement
readings are provided through standard 4-20mA 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
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 Herriott 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 (see Technology for
more information).
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.
Table of Gases
|
Gas
|
Detection limit
|
Min meas. range
|
|
|
|
O2
|
1 ppm
|
1.5 mg/m3
|
0 - 150 mg/m3
|
|
|
|
H2O
|
0.003 ppm
|
0.002 mg/m3
|
0 - 0.2 mg/m3 *
|
|
|
|
H2S
|
0.3 ppm
|
0.45 mg/m3
|
0 - 40 mg/m3
|
|
|
|
CH4
|
0.02 ppm
|
0.014 mg/m3
|
0 - 2 mg/m3
|
|
|
|
CO
|
3 ppm
|
4 mg/m3
|
0 - 400 mg/m3
|
|
|
|
CO2
|
3 ppm
|
6 mg/m3
|
0 - 600 mg/m3
|
|
|
|
CO (low conc)
|
0.03 ppm
|
0.04 mg/m3
|
0 - 4 mg/m3
|
|
|
|
CO2 (low conc)
|
0.02 ppm
|
0.04 mg/m3
|
0 - 4 mg/m3
|
|
|
|
NO
|
1.5 ppm
|
2 mg/m3
|
0 - 200 mg/m3
|
|
|
|
N2O
|
0.5 ppm
|
1 mg/m3
|
0 - 100 mg/m3
|
|
|
|
NH3
|
0.015 ppm
|
0.011 mg/m3
|
0 - 1.5 mg/m3
|
|
|
|
HCl
|
0.005 ppm
|
0.008 mg/m3
|
0 - 0.8 mg/m3
|
|
|
|
HF
|
0.0015 ppm
|
0.0013 mg/m3
|
0 - 0.15 mg/m3
|
|
|
|
HCN
|
0.03 ppm
|
0.04 mg/m3
|
0 - 4 mg/m3
|
NOTE: Detection limits are specified as two standard deviations
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
are available on request.
Data sheet for
download
LaserGas
II Multipass (Acrobat 280751 bytes)(.pdf)