Visibility measurement and fog detection

The sensor uses the forward scatter measuring method to determine the meteorological optical range.

The transmitter on one side emits light which is scattered by particles in the air. The receiver on the other side receives the share of the light which is scattered at an angle 39° to 51°. The intensity of the received light is used to calculate the meteorological optical range.

The unique design ensures that the output is both accurate and reliable in all weather conditions and will not be influenced by local lights sources, even those that flash.

With a measuring range of 10 m to 40 km the sensor is suitable for use in road and aviation applications as well as meteorological observation networks. Whilst the measurement accuracy easily exceeds that specified by ICAO for visibility sensors used in METAR and RVR applications.

Heating of the optical windows and sensor hoods is provided as standard allowing use in the harshest of conditions. Both optical windows are monitored for contamination and the visibility output is automatically compensated to reduce maintenance requirements.

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w/MOR Visibility Sensor

  • Visibility sensor using forward scattering to measure the meteorological optical range
  • 10 m to 40 km measuring range
  • Hood and windows heated
  • Comprehensive self-test and maintenance data
  • Optical windows monitored for contamination
  • Optional ambient light sensor
  • RS-232, RS-422 and RS-485 interface
  • Automatic or polled mode
  • Optional analogue output
  • Visibility sensor to be mounted on pole or wall
  • Connection to control system by RS-485, RS-422 or RS-232
  • openWIS Plugin
  • Compact forward scatter design
  • Not affected by local lights
  • Easily installed by one person
  • Hood heating for use in extreme environments
  • Flexible integration into control system
  • openWIS compatible
Technical Specifications
Visibility measurement
Measuring method Forward light scattering with 39° to 51°angle
Measured values Visibility (MOR)
Extinction coefficient
Measuring range 10 m .. 40 km
Accuracy ≤ 4.5% at 600m, ≤ 5.0% at 1,500m, ≤ 5.1% at 2km, ≤ 12.5% at 15km, ≤ 20% at 30km
Type w/MOR (BIRAL SWS-050)
Operating voltage 9 .. 36 VDC
Hood heating 24 VDC or 24 VAC
Power consumption 3.5 W (sensor)
1.7 W (window heaters)
24 W (hood heaters)
Housing material Powder coated aluminium
Dimensions 811 x 315 x 329 mm
Weight 4.3 kg
Protection class IP66
Temperature range -40 .. 60 °C
Analogue output 4-20 mA (optional)
Digital interface RS-232, RS-422 or RS-485
Interface modes Polled or automatic
Output rate 10 .. 300 s (automatic mode)
Electrical standards 2014/30/EC EMC directive
2014/35/EC Low voltage directive
Road safety AT: RVS 12.04.14 Straßenzustandsinformationssysteme für den Winterdienst (November 2014)
DE: Technische Lieferbedingungen für Streckenstationen Ausgabe 2012 (TLS 2012)


Produktinfo DE (PDF, 450 kB)
Produktinfo EN (PDF, 457 kB)
RVS Konformitätserklärung DE (PDF, 248 kB)