Bristol Industrial & Research Associates Ltd (BIRAL)

- Model 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

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  :  6°
  • 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

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