Senseca

ALS-2 Ambient Light Sensor

Ambient light sensor for runway visual range (RVR) systems.

Measures background luminance 0…40,000 cd m-2 with 1 cd m-2 resolution and 6° field of view
RS232, RS422 or RS485 serial outputs, with direct connection to Senseca visibility and present weather sensors
Heated window and window contamination monitoring as standard, designed to ICAO, WMO and FAA guidance

Quantity

Overview

The Senseca ALS-2 Ambient Light Sensor measures background luminance as part of an instrumented Runway Visual Range (RVR) system. Mounted alongside the runway and typically deployed with a visibility sensor, it provides the ambient light data required for accurate RVR calculation, and it is designed to comply with ICAO, WMO and FAA specifications and guidelines for typical aviation RVR systems. The ALS-2 can operate standalone with RS232, RS422 or RS485 serial outputs, or connect directly to a Senseca visibility or present weather sensor, where its luminance values are embedded in the host sensor's data string for a single integrated output, making it suitable for both new and legacy installations. Built for continuous outdoor use with low maintenance, it has a heated window, window contamination monitoring and compensation, and extensive self-test functions, and can be checked and calibrated on site with the ALS-2 CAL field calibrator.

Typical applications

Instrumented Runway Visual Range (RVR) systems
Background luminance measurement alongside airport runways
Use with Senseca visibility and present weather sensors
New and legacy (retrofit) RVR installations

Key Features

Background luminance measurement 0…40,000 cd m-2, 1 cd m-2 resolution
6° field of view, 60 s averaging period
Spectral response 420…675 nm, peak 565 nm, analogous to CIE luminous spectral efficiency
RS232, RS422 or RS485 serial outputs; optional dual 0–10 V analog outputs (low mode 0…4,000 cd m-2, high mode 0…40,000 cd m-2)
Direct connection to Senseca visibility and present weather sensors
Window heater and window contamination monitoring and compensation fitted as standard
Optional heated hood to prevent snow accumulating around the optical window
Pole-mounting bracket with 0° to 45° elevation adjustment and integral alignment scale
In-field calibration with the ALS-2 CAL calibrator via IR link

Benefits

Designed to FAA and ICAO requirements for aviation RVR systems
0 to 40,000 cd m-2 measurement range
Choice of serial digital RS232 or RS422 outputs
Simple and quick in-field calibration
Direct connection to Senseca visibility and present weather sensors
Extensive self-test capabilities
-60 °C to +70 °C operating range with extended heating

Specifications

MEASUREMENT SPECIFICATIONS
Measures	Luminance (ambient light)
Output	Serial data
Measurement range	0…40,000 cd m-2 (0…11,700 fL)
Resolution	1 cd m-2 (0.29 fL)
Measurement error	≤ 10% of value or 2 cd m-2 (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

OUTPUTS
Serial data outputs	RS232, RS422 or RS485
Baud rates	1200 Baud to 38K4 Baud, user selectable
Analog output (option)	Low mode 0–10 V proportional to 0…4,000 cd m-2 High mode 0–10 V proportional to 0…40,000 cd m-2

POWER REQUIREMENTS
Sensor power	9…36 Vdc
Hood heating power	24 Vac or dc
Sensor & window heater	2 W
Hood heater	12 W
Extended heating	18 W (includes hood heater)

ADDITIONAL FEATURES
Window heater	Fitted as standard
Window contamination monitoring and compensation	Fitted as standard

ENVIRONMENTAL
Operating temperature	-40 °C to +70 °C
Operating temperature with extended heating	-60 °C to +70 °C
Operating humidity	0…100% RH
Protection degree	IP 65

PHYSICAL
Material	Aluminium. Powder paint finish, with hard anodize base layer
Weight	1.5 kg
Elevation angle range from horizontal	0° to 45°
Mounting	Pole mounting bracket for vertical poles with 40…64 mm outer diameter (U-bolt and saddle supplied)
Lifetime	> 10 years

CERTIFICATION & COMPLIANCE
Compliance	CE certified EMC compliance with EN61326-1997, 1998, 2001 RoHS and WEEE compliant

ORDERING CODES	ALS2. [Hood heating] . [Data output] . [Configuration] Example: ALS2.HV.D.RC
Hood heating	EH = Extended heating HV = With heating NH = Without heating
Data output	B = VPF connector, 1.5 m cable with connector D = SWS/RS232 output, 1.5 m cable with flying leads E = RS422/RS485 output, 1.5 m cable with flying leads
Configuration	RC = regular configuration SC = special configuration
Accessories (optional)	ALS-2.CAL = Ambient Light Sensor Calibrator ALS2.WTY = 1 year extended warranty
Supplied with	Pole mounting kit (1 x U-bolt and saddle), user manual and calibration certificates, in recyclable foam filled packaging

Drawing

Downloads

ALS-2 Family Datasheet (EN)	DownloadALS-2 Family Datasheet (EN)
ALS-2 CAL Calibrator Datasheet (EN)	DownloadALS-2 CAL Calibrator Datasheet (EN)
ALS-2 Family User Manual (EN)	DownloadALS-2 Family User Manual (EN)