DT027 Delta-T BF5 Sunshine Sensor

Two analogue voltage outputs give global and diffuse radiation, from which direct and diffuse radiation are derived. The sunshine state is indicated by a digital output. The three outputs can be connected to appropriate channels on the GP1 or GP2 data loggers, or other loggers commonly used for environmental monitoring. An internal heater keeps the BF5 Sunshine Sensor clear of dew, ice and snow down to -20 °C.

Sunshine Duration
The BF5 Sunshine Sensor measures sunshine hours indirectly using a simple equation based on the total PAR radiation (Photosynthetically Active Radiation), and the ratio of total to direct PAR. This sunshine algorithm corresponds closely to the World Met Office threshold of 120 W/m-2 in the solar beam for sunshine duration. The BF5 Sunshine Sensor does not need to be adjusted or repositioned to track the sun – a distinct advantage over devices with shadow rings. There are no complex electro-mechanical assemblies and no burnt paper tracks to interpret.

SunScan Canopy Analysis System
The BF5 Sunshine Sensor can be used as an integral component of the SunScan Canopy Analysis system. The SunScan Probe is a 1 m long light sensor array suitable for measuring PAR interception by plant canopies and estimating LAI (Leaf Area Index). The BF5 Sunshine Sensor improves the accuracy of the SunScan system and enables it to be used even under variable light conditions.

Applications
In addition to its role in the SunScan System, the BF5 Sunshine Sensor’s alternative outputs enable it to be used in the study of photosynthesis, illumination and solar energy measurement.

For building energy management systems (BEMS), the BF5 can be used to control the opening and closing of blinds or louvres in response to sunlight. The BF5’s ability to measure both the energy in the direct beam and also total radiation, makes it possible to optimise the use of natural light and solar gain while minimising glare for the building’s occupants.

Comparison with SPN1 Sunshine Pyranometer
The SPN1 Sunshine Pyranometer is a precision version of the BF5 Sunshine Sensor and although the two instruments have some features in common, there are important differences. These are summarised in the document: “SPN1 and BF5 Comparison Data Sheet“.