Visibility and present weather detection

The sensor is optimised for use in aviation applications where both visibility and extended present and past weather information is required. It measures measures visibility, fog, haze, drizzle, snow, hail and other non-frozen precipitation according to WMO table 4680. METAR coded outputs are also provided.

For ultimate visibility performance the visual range extends to 75km allowing use in meteorological observation networks and research applications.

The enhanced present weather information is due to the backscatter receiver which allows detailed precipitation analysis.

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

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.

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w/PWD Present weather detector

  • Visibility sensor using forward and backward scattering to measure the meteorological optical range and detect the present weather
  • 10 m to 75 km measuring range
  • Instantaneous and averaged visibility outputs
  • Present and past weather by 34 METAR codes
  • 39 WMO 4680 codes
  • 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
  • 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 and back scatter design
  • Detailed classification of precipitation
  • Not affected by local lights
  • Simple field calibration
  • Hood heating for use in extreme environments
  • Easily installed by one person
  • Flexible integration into control system
  • openWIS compatible
Technical Specifications
Visibility & present weather detection
Measuring method Forward light scattering with 39° to 51°angle and backward light scattering
Measured values Visibility (MOR)
Extinction coefficient
Transmission equivalent extinction coefficient
Present weather (WMO 4680, METAR)
Precipitation intensity
Measuring range 10 m .. 75 km (MOR)
0 .. 500 mm/hr (rain intensity)
Accuracy ≤ 4.5% at 600m, ≤ 5.0% at 1,500m, ≤ 5.1% at 2km, ≤ 12.5% at 15km, ≤ 20% at 30km (MOR)
≤ 15 % (rain intensity)
Precipitation detection threshold Rain: 0.015 mm/hr
Snow: 0.0015 mm/hr
Type w/PWD (BIRAL SWS-250)
Operating voltage 9 .. 36 VDC
Hood heating 24 VDC or 24 VAC
Power consumption 3.5 W (sensor)
2.5 W (window heaters)
36 W (hood heaters)
Housing material Powder coated aluminium
Dimensions 811 x 315 x 329 mm
Weight 3.5 kg
Protection class IP66
Temperature range -40 .. 60 °C
Digital interface RS-232, RS-422 or RS-485
Interface modes Polled or automatic
Output rate 10 .. 300 s (automatic mode)
WMO codes 39 from table 4680
METAR codes 34 present and past weather
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)


Product info DE (PDF, 539 kB)
Product info EN (PDF, 527 kB)
RVS Konformitätserklärung DE (PDF, 248 kB)