The laser diode gas analyzer SITRANS SL

SITRANS SL is designed for measuring oxygen (O2) with high sensitivity. It consists of a pair of cross-duct sensors, a transmitter unit and a detector unit, both with the same dimensions. Due to its little installation effort and its minimum maintenance requirements, SITRANS SL guarantees a high level of economic efficiency.

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Laser diode gas analyzer

SITRANS SL – easy to handle with contact-free measurement

The gas analyzer SITRANS SL consists of a pair of cross-duct sensors, a transmitter unit and a detector unit, both with the same dimensions. The sensors (transmitter and receiver) are meant to be mounted directly on the process with no need of sampling systems. The hardware for processing the measurement signal into a concentration value as well as monitoring, control and serving of the communication means are also integrated into these two main modules. The sensors are designed for operation under harsh environmental conditions. Laser light is sent from the transmitter, passing through the process gas, arriving at the detector on the receiver side. The measurements are carried out on-line with a very short response time permitting fast and effective cost-savings in process control. The laser characteristics allow single-line spectroscopy free of interferences. Since the band width of the laser light is extremely narrow, only the gas component of interest will interact with it. Other process influences, such as dust and temperature, are easily eliminated due to the excellent inherent compensation capabilities of this technique.

High functionality with remote control

The detector unit is connected to the transmitter unit by means of a sensor cable. A further cable on the receiver is used to connect the power supply and the communication interfaces. The receiver enclosure contains a local user interface (LUI) with an LC display which can be read through a window in the cover. The LUI is operated by remote control.

Innovative solution for calibration

An in-line reference cell filled with a non-interfering reference gas, a further development of the already established Siemens TDL technology, provides unique user benefit in terms of minimum need for maintenance and recalibration. 


  • Process control (chemical industry) 
  • Process optimization (steel industry)
  • Safety monitoring, e.g. measuring minimum or maximum concentration limit for oxygen in explosive proof environment
  • Combustion control (boilers, municipal waste incinerators) 

Technical data

Max. number of components 
Smallest measuring range 
O2: 0-1 Vol%
field version

Benefits at a glance

  • Little installation effort 
  • Minimum maintenance requirements 
  • Extremely rugged design 
  • High long-term stability through built-in, maintenance-free reference gas cell 
  • Real-time measurements 
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Safety is key in the process industries. A failure in instruments relevant for safety may have serious implications for humans, the process and the environment. Therefore, a wide range of our process instruments come with on-board safety features for maximum risk reduction.


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