Laser Multipass Analyser

 LASERGAS^TM 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

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.