SWS-100LW Visibility Sensor

The SWS-100LW is optimised for use in applications where accurate and reliable visibility measurements are required from a low power, light weight sensor
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The SWS-100LW is optimised for use in applications where accurate and reliable visibility measurements are required from a low power, light weight sensor.

When only solar power is available or when reliance on batteries is essential the SWS-100LW is the perfect choice for a fully featured visibility sensor. With a power consumption of just 2.9W the sensor places a minimum burden on the supply system and can be intermittently powered for even lower power consumption. The physical design has been optimised to reduce both the size and weight whilst retaining the performance and robustness expected of a Biral visibility sensor.

This high quality sensor includes a remote monitoring and self-test system that is essential for high integrity systems. Connectivity is provided through a military style circular connector with RS232 communications.

For use in aviation applications the sensor can optionally be fitted with an interface to the ALS-2 Ambient Light Sensor.

  • 2.9W Power consumption
  • Light weight 2.7kg
  • 10m to 75km measurement range (other ranges available)
  • Limited WMO 4680 present weather codes
  • Compact forward scatter design
  • Window heating and contamination monitoring
  • Comprehensive self-test capabilities
  • Serial data output (RS232, RS422 or RS485)
  • Compatible with ALS-2 Ambient Light Sensor

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Technical Description

The SWS-100LW

The SWS-100LW was developed as a tactical sensor for use by special forces. The power consumption has been reduced to allow operation from batteries or combined solar PV panels and batteries. The enclosure has been redesigned to provide a lightweight yet robust sensor that is also smaller than the standard SWS-100. Whilst initially designed for use by special forces the features of the SWS-100LW make it suitable for use wherever a high quality, lightweight low power visibility sensor is required.

The 45° forward scatter angle and 850nm infrared light source used by the SWS-100LW provide the best possible visibility measurement accuracy in all weather conditions. Visibility is output as Meteorological Optical Range (MOR) whilst World Meteorological Organisation (WMO) Table 4680 codes are used to report present weather.

In common with all Biral visibility and present weather sensors the SWS-100 uses 2kHz modulation of the light source combined with narrow pass band optical filters and synchronous detection at the receiver to ensure the measurement is not affected by bright or flashing lights. This design also ensures the sensor accurately reports visibility during precipitation whilst allowing the accurate reporting of drizzle, rain and snow. The horizontal hood design eliminates the problems caused by surface reflections that are a source of error in sensors employing look down hood geometries.

The optical windows of the sensor are fitted with low power heaters to prevent the formation of condensation. Window contamination monitoring and compensation allows the visibility output to maintain its accuracy even as dirt builds up on the optical surfaces. The sensor reports the window contamination in the output message using two stages of warning flags allowing cleaning to take place in a convenient manner.

Communication with the sensor is over a serial RS232 data link. ASCII encoded data is used and the sensor can operate in either a polled or broadcast modes. The data message can include a time stamp from the internal real time clock in addition to the standard visibility, present weather and basic self-test information.

The sensor operates from a low voltage DC supply and requires just 2.9W. The low power window heaters that can be set to only operate when condensation is detected take an additional 1.7W.

The SWS-100LW is a single lightweight unit that can be easily transported and installed by one person. The sensor enclosure is constructed from aluminium which is surface passivated and finished with a powder coat paint. It is designed for use in all types of weather and has a wide operating temperature.


Visibility, MOR
Present weather (Drizzle, Rain and Snow)
Measurement Principle
Forward scatter 45°
Measurement Error
5% at 1,500m
Sensor Power
9 – 36 V DC (2W)
Window heating and contamination monitoring
Operating Temperature
-40°C to 60°C
Operating Humidity
0 – 100% RH
Protection rating
2.7 kg


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.

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