ALS-2 Ambient Light Sensor


The ALS-2 Ambient Light Sensor is designed to measure background luminance as part of a Runway Visual Range (RVR) system. Mounted alongside the runway the ambient light sensor is often deployed with a visibility meter to provide the data necessary for calculation of RVR.

Designed to comply with specifications and guidelines produced by the International Civil Aviation Organisation (ICAO), World Meteorological Organisation (WMO) and the Federal Aviation Administration in the USA (FAA), the ALS-2 meets all the requirements for use in typical RVR systems. The ability to connect the sensor directly to a Biral visibility or present weather sensor and have the background luminance data incorporated into the visibility sensors data string simplifies system design and construction.

  • Designed to FAA and ICAO requirements
  • 2 to 40,000 Cdm-2 measurement range
  • Choice of serial digital or analogue outputs
  • Simple and quick in field calibration using our automatic calibration device (ALS-CAL)
  • Direct connection to Biral visibility and present weather sensors
  • Extensive self-test capabilities
  • -60°C to 70°C operating range
  • This product is certified for use in Russia by Rosstandart – the Federal Agency for Technical Regulation and Metrology.


  • Measures Luminance (ambient light)
  • Output Serial data. Optional analogue outputs
  • Measurement range: Serial Data:  0-40,000 cd m
  • Analogue outputs: 0-4,000 cd m (Low output); 0-40,000 cd m (High output)
  • Resolution 1 cd m (0.29 fL)
  • Measurement error ≤ 10% of value or 2 cd m (0.58 fL), whichever is greatest
  • Spectral response Wavelength sensitivity range 420-675 nm, peak 565 nm.
  • Analogous to CIE luminous spectral efficiency.
  • Field of view 6°
  • Averaging period 60 s


  • Serial data outputs RS232, RS422 OR RS485
  • Analogue outputs: (Option) 2 voltage outputs, high and low range, 0-10 Vdc


  • Sensor Power 9-36Vdc
  • Hood heating power 24Vac or dc
  • Sensor & window heater 2W
  • Hood heater 12W
  • Extended heating 18W (includes hood heater)


  • Window heater Fitted as standard
  • Window contamination monitoring and compensation Fitted as standard


  • Operating temperature
  • With extended heating
  • -40°C to +70°C
  • -60°C to +70°C
  • Operating humidity 0 – 100% RH
  • Protection rating IP66


  • CE Certified
  • EMC compliance with EN61326-1997, 1998, 2001
  • RoHS and WEEE compliant
  • Material Aluminium. Powder paint finish, with
  • hard anodize base layer
  • Weight 1.5kg
  • Elevation angle range from horizontal 0° to 45°
  • Warranty 2 years
  • Lifetime >10 years


  • Self-test capability As standard
  • User confidence check 6 months recommended
  • Window Cleaning Automatic compensation and warnings
  • Field calibration With optional calibration kit


The sensor is delivered in sturdy recyclable foam filled packaging with:

  • Pole mounting kit (1 x U-bolt and saddle)
  • User manual and calibration certificates


  • ALS-2.CAL Ambient Light Sensor Calibrator
  • ALS2.WTY 1 Year Extended Warranty