Unique Sensor Design

The Sunshine Sensor is a patented design*. It uses an array of photodiodes with a unique computer-generated shading pattern to measure incident solar radiation. A microprocessor calculates the Global and Diffuse components of the radiation and determines the sunshine status. A built-in heater keeps the BF5 clear of dew, ice and snow down to -20°C.
* The Sunshine Sensor is protected by patents EP 1012633 & US 6417500


Two analogue voltage outputs are provided for the Global and Diffuse radiation. The sunshine state is represented by a digital output (contact closure). The three outputs can be connected to appropriate channels on data loggers e.g. the Delta-T logger type DL2e, or other loggers commonly used for environmental monitoring.


The BF5 sensor can be used as an additional sensor with a conventional Met Station. The weather station logger is used to record Global (Total) and Diffuse radiation and the sunshine state (or duration). Power for the sensor comes from its internal alkaline batteries or alternatively from the weather station logger battery. Typically the data will be used for Global and Diffuse radiation, and the sunshine hours during the day (see chart opposite). Direct beam radiation is calculated from Total minus Diffuse. Radiation output units can be preset to energy or PAR or illuminance.


  • Measures Global (Total) and Diffuse radiation
  • Measures Sunshine duration
  • No routine adjustment or polar alignment
  • No moving parts, no shade rings
  • Outputs can be set to Energy (W.m-2)
    PAR (┬Ámol.m-2.s-1), or Lux
Accuracy: Sunshine Hours ±10% (WMO definition)
Accuracy: Cosine Correction ±10% of incoming radiation over 0 - 90º Zenith angle
Accuracy: Azimuth Angle ±5% over 360º rotation
Temperature Coefficient ±0.15% / º C typical
Temperature Range

-20 to +50º C, Alkaline batteries

-20 to 79º C, Lithium batteries

Recommended Recalibration Interval 2 years
Response Time < 250 ms
Spectral Response 400 - 700 nm
Latitude Capibility -90º to 90º
Environmental: Sealing IP65 (shower and dust proof)
Sunshine Status: Contact Closure

No sun = open circuit

Sun = short circuit to ground

Internal Battery 2 x 1.5 V AA Alkaline batteries
Power Requirement 2 mA, (awake), <30 A (asleep)
Battery Lifetime 1 year typical