Gas flow measuring instruments

Your Benefits

  • Representative measurement across total tunnel width
  • Very reliable measurement, compared with punctual measurement methods
  • Accurate measurement even of very low flow velocities
  • Long maintenance intervals of up to 5 years
  • Low operating costs due to reliable operation and low maintenance
  • High availability of devices and, therefore, of measurement data also

The exact device specifications and performance data of the product may deviate from the information provided here, and depend on the application in which the product is being used and the relevant customer specifications.
In accordance with Article 2 (4), this product does not fall within the scope of RoHS directive 2011/65/EU and is also not designed for use in products which fall within the scope of this directive. You can find additional information in the product information.


The FLOWSIC200 is used for the contact-free and accurate measurement of flow velocity and flow direction inside tunnels or exhaust ventilation ducts. Ultrasonic technology provides the cross-sectional mean average value of the flow velocity. This device is used for measurement necessary for optimal ventilation control and reducing running costs to a minimum when air flow is dictated by climatic conditions or by traffic.

In case of fires in tunnels the accurate, reliable and representative measurement of air velocity and direction across the tunnel is mandatory. This is the only way to check reliably the smoke propagation and to achieve the necessary information for optimal control of the ventilation system.

At a glance
  • Very large measuring distances possible
  • Non-contact measurement
  • Extremely rugged components made of titanium, stainless steel, or die cast
  • Versions for very corrosive tunnel atmospheres
  • Determination of flow direction
  • No mechanical moving parts


Reliable tunnel ventilation - even in the event of fire

The FLOWSIC200 reliably and accurately measures the air flow in road or train tunnels. Using the FLOWSIC200, ventilation systems in tunnels are controlled and sufficient aeration and ventilation of the tunnel is ensured over the long term. Thanks to the FLOWSIC200’s rugged ultrasonic technology, differences in density and temperature fluctuations in the tunnel air do not influence the measurement result. This means that the measuring function of the FLOWSIC200 remains intact if the dynamics of the flow completely change within a short time as a consequence of a tunnel fire. The function proved to be without constraints during fire testing with the Forschungsgesellschaft für Verbrennungskraftmaschinen und Thermodynamik mbH (FVT mbH) Austria.

Air flow velocity monitoring in road and rail tunnels is a key component of ventilation technology in tunnel systems. Measurement of the air flow is subject to strict requirements. The measuring technology used must reliably and accurately measure the flow in the tunnel cross section, even when there is varying traffic volume. In order to avoid traffic interruptions, maintenance work on the measuring device must be kept to a minimum.

Measuring conditions completely change in the event of a fire in the tunnel. A large amount of thick smoke can develop in a short time. The gas composition changes significantly. The temperature increases very quickly at the site of the fire. The overall thermodynamic situation leads to a considerable change in the flow dynamics at the fire source. The FLOWSIC200 also works reliably under these extreme conditions - transmission of the acoustic signal is ensured at all times due to the integrated automatic signal amplification.

Rugged, reliable, powerful.

Tunnel installations such as fans or illumination do not affect the measurement result.
Functional testing in tunnel fire assessments of the Klaus tunnel system on the A9 highway in Upper Austria.

Exceptional performance and durability even under demanding measurement conditions characterize the FLOWSIC200.


The FLOWSIC200 consists of the ultrasonic sensors and the MCU control unit. SICK offers the device in 3 versions for tunnel widths of up to 35 m. Thanks to rugged stainless steel or aluminum die-cast components, the FLOWSIC200 has a clear advantage in the event of a fire compared to conventional measuring technology made from plastic.

The MCU control unit is used to input and output signals and permits simple connection of the FLOWSIC200 to higher-level distributed control systems. Different interfaces are available for this which can be optionally expanded if necessary. An periodic control cycle checks the device function completely automatically, while the integrated self-diagnosis continuously monitors all important function parameters.

Compact and intuitive.

Principle of operation of the FLOWSIC200
Reliable signal transmission thanks to fully-automatic gain control



Technical overview

  • Technical data overview

    Technical data overview

    Measurement principleUltrasonic transit time difference measurement

    RABT 2006

    ASTRA "Guideline - Ventilation of Road Tunnels" (2008)

    RVS 09.02.22

    Enclosure rating

    Sender/receiver units: IP66

    MCU control unit: IP65

    FunctionConnection to SOPAS ET software
    Serial✔ , ✔
    Type of fieldbus integrationRS-232
    FunctionConnection to SOPAS ET software
    Internal system bus
    Type of fieldbus integrationRTU RS-485
    Diagnostics functionsInternal zero and reference point check
All technical data can be found accompanying the individual product