Optical Sensors / CS140
CS140 Background Luminance Sensor
High-Performance Sensor at an Economical Price
weather applications supported water applications supported energy applications supported gas flux and turbulence applications supported infrastructure applications supported soil applications supported


The CS140 is a high-quality background luminance sensor. It provides the luminance data required to assess the visibility range for lights such as runway lights or warning lights.

The field of view and elevation angle follow aviation practice, and the spectral response follows the CIE curve that matches the typical response of the human eye.

The CS140 meets the standards required for Runway Visual Range, as well as the standards of ICAO, the UK CAA and the FAA. (This includes CAP670 and CAP746.)

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Benefits and Features

  • Monitoring of internal supply voltages and temperatures
  • Elevated field of view with hood horizontal to give high resistance to contamination on the window
  • RS232/RS485 outputs so can operate independently of a host visibility sensor for flexible, reliable operation
  • Automatic window contamination detection
  • Configurable window contamination correction
  • High performance sensor at a competitive price
  • Incorporates automatic dew and hood heaters for all-weather operation
  • Low power consumption; suitable for solar power applications
  • Made in UK
  • Three year extended warranty available on this product
  • Type certified for Aviation use by the German Meteorological Service, Deutscher Wetterdienst (DWD)


CS140 with sensor cable, heater cable, and mounting kit
CS140 with sensor cable, heater cable, and mounting kit
CS140 with sensor cable, heater cable, and mounting kit

Technical Description

The CS140 Background Luminance Sensor accurately measures background luminance over a wide range from 0 cd/m2 to a maximum of 45,000 cd/m2

The CS140 uses a photodiode with a spectral response close to the CIE human eye model and removes any unwanted wavelengths via an inbuilt band-pass filter.

The CS140 features a fixed 6˚ field of view as specified by the FAA. For ease of installation, the CS140 is simply mounted horizontally with the required 6˚ inclination already built into the design. (Other angles are possible via the sensor mounting bracket.)

The CS140 features a heated hood to prevent ice and snow from building up, dew heaters to prevent condensation on the glass window, and a dirty window detection system to measure window contamination.

The design is undamaged when pointed directly at the sun, allowing complete flexibility in orientation.

The CS140 has a rugged IP66 rated environmental enclosure that protects it from the harshest conditions and measures the atmosphere with high stability and repeatability.


Measurement Range 0 to 45,000 cd/m2
  • ±0.2cd/m2 (< 2cd/m2)
  • ±10% (> 2cd/m2)
Operating Temperature
  • -25° to +60°C (standard)
  • -40° to +70°C (extended, optional)
Operating Humidity 0 to 100%
Wind Speed Up to 60 m/s
Sensor Sealing Rated to IP66
Response Time 1 s
Mountings Stainless-steel V-bolt mounting to pole
Diameter 3.2 to 5.25 cm (1.26 to 2.07 in.)
Sensor Dimensions 36 x 18 x 9 cm (14.2 x 7.1 x 3.5 in.)
Weight ~2.4 kg (~5.3 lb) dependent upon mounting system
Shipping Weight 3.5 kg (7.7 lb)


-NOTE- Lower power states can be achieved by less frequent sampling and remote control of heaters.

Optional power supplies with battery back-up available.

A low-voltage shutdown level can be set to prevent back-up batteries from being damaged.
Electronics Supply Voltage 9 to 24 Vdc
Hood Heater Supply Voltage 24 V dc or ac
Hood Heater Power 48 W
Dew Heater Power 0.6 W
Total Unit Power < 1.5 W while sampling continously (including dew heater)


Serial Interface
  • RS-232 (full duplex, no hardware handshaking)
  • RS-485 (half duplex only)
Serial Data Rates 1200 to 115,200 bps (38,400 bps default rate)


-NOTE- Lens contamination circuitry monitors the window for contamination. The sensor can be configured to adjust calibration for contamination.
Field of View (FOV) 6° wide with sharp cut-off
Elevation Angle 6° with hood horizontal
Resolution 0.1 cd/m2


Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.


Product Compatible Note
CR1000 (retired)
CR200X (retired)
CR216X (retired)
CR300 Using the CR300 with the CS140 is not recommended, as this would use the only RS-232 connection on the data logger.
CR310 Using the CR310 with the CS140 is not recommended, as this would use the only RS-232 connection on the data logger.
CR350 Using the CR350 with the CS140 is not recommended, as this would use the only RS-232 connection on the data logger.
CR5000 (retired)
CR800 (retired)
CR850 (retired)
CR9000X (retired)

Additional Compatibility Information

Datalogger Considerations

This sensor is compatible with any datalogger with a serial input.


CS140 Program Examples (5 KB) 15-03-2022

Four example CR1000X programs are included that use the POLL, SET, SETNC, and GET commands for the CS140. Other data loggers are programmed similarly.

CS140-OS Release 10 v.10 (53 kB) 09-03-2021

Release Note for Operating System OS10 for the Campbell Scientific CS140 Background Luminance Sensor

Campbell Scientific has introduced a new operating system, OS10, for the CS140 background luminance sensor. It is fully backwards compatible and is easily installed on all CS140 sensors. OS10 is available free of charge and can be downloaded from the Campbell Scientific website or supplied by email on request. Functionality, including data message formats is unchanged.

Main improvements:

  • Bug fixed relating to the main serial communications baud rate and particular versions of CPU silicon.
  • Timing bug in RS485 fixed to improve compatibility with certain RS485 interfaces.

Case Studies

Instrumented Runway Visual Range (IRVR) System for Civil Aviation
Exeter Airport is undergoing a huge refurbishment to expand their capabilities and streamline their operations......read more
Central Africa: Airport Weather System
Campbell Scientific’s system integrator, AUDIMOBIL LDA, recently upgraded the airport weather system in the S.......read more

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