SITRANS SL is a diode laser gas analyzer with a measuring principle based on the specific light absorption of different gas components. SITRANS SL is suitable for fast and non-contact measurement of gas concentrations in process or flue gases. 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.

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)



Max. number of components




Smallest measuring range

O2: 0-1%


Field version


  • 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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