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The BF5 Sunshine Sensor measures Global and Diffuse radiation and sunshine duration

  • No routine adjustment or polar alignment
  • No moving parts, no shade rings
  • Outputs can be set to Energy (W.m-2), PAR (μmol.m-2.s-1) or Lux

Unique 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 GP2, 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.

BF5 Specifications

The BF5 is intended for use outdoors in natural daylight, with an unobstructed view of the horizon. Significant errors may be produced by artificial light, or if the BF5 is shaded from direct sunlight by buildings, or if there are strong reflections, from windows, for example. The following accuracy figures give 95% confidence limits, i.e. 95% of individual readings will be within the stated limits under normal climatic conditions.