ALS-2 Ambient Light Sensor

Model Number: ALS-2
Manufacturer: Biral
Product Brochure: Download

Accurate and reliable determination of background light during all weather conditions


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
  • 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.

Technical Description

With a spectral response that approximates that of the eye and a 6° field of view the ALS-2 is designed to meet international requirements for background luminance measurement including those of the FAA and ICAO. This sophisticated sensor provides 60s averaged data and incorporates a wide range of self-test and monitoring features.

Available with a choice of serial data or analogue outputs the ALS-2 can be used to replace a wide range of background luminance meters in both legacy and new installations. The simple pole mounting system even incorporates an angular scale to ease installation.

A unique feature of the ALS-2 is its ability to be calibrated in the field without the need to disconnect the cable or send commands via the software interface. The ALS-2 Field Calibrator accessory simply fits over the hood and communicates with the sensor using an IR link through the optical window. The calibration can be checked and adjusted in a matter of minutes without the need for specialist staff or laboratory equipment.

Designed to operate in the harshest of weather the ALS-2 has window heating and window contamination adjustment as standard. Optional hood heating completes the package.


Measurement Background luminance 2-40,000 Cdm-2 (0.5-11,700 fL)
Serial Output RS232, RS422
Analogue Output Optional - 2 x Analogue outputs
Low Output 2-4,000 Cdm-2 High Output 20-40,000 Cdm-2
Spectral Response Wavelength sensitivity range 420-675 nm, peak 565 nm. Analogous to CIE luminous spectral efficiency
Measurement Error <10%
Field of View
Averaging Period 60s
Sensor Power 9-36 V DC (2W)
Hood Heating Power 12W (24V AC or DC)
Window heating and contamination monitoring Fitted
Operating Temperature -40°C to 70°C, -60°C to 70°C (With extended heating Option)
Operating Humidity 0 – 100% RH
Protection rating IP66
Weight (Sensor Head) 1.5kg


Application notes, white papers and other publications relating to this product can be found in our resource area


Sales & Support

Contact Biral for more information

To find out more about this instrument or to discuss your application requirements please do not hesitate to contact Biral.

After Sales Support

Biral offers free advice and technical support for the lifetime of the instruments we sell. Once you have purchased the unit you can always contact us for help using the links on our Service Support page.