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.
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.