DPD504.1 Sunshine Duration (MTI.AWS.LS.504.1) rotation band sunshine duration sensor The sensor measures sunshine duration and direct radiation from the sun. Measurement is made in the visible range and near infrared, to second class WMO pyranometer specifications. Once set up for the latitude and location, the sensor does not require seasonal positioning unless greater precision is needed, accomplished by two annual adjustments. For each rotation, the instrument determines the two radiation levels of the beam, with and without the direct action of the sun disc, and calculates the difference, which gives a good approximation to the direct radiation level. The instrument also supplies the sunshine duration, defined by World Meteorological Organization (WMO, 1981) as the time during which the direct solar radiation exceeds the level of 120 W/m², and is normally measured in hours. The sensor has two actionable heaters: a continuous anti-condensation heater and a thermostatic one for defrosting. In conditions of darkness, the band is stopped and the sunshine status is set to “no”.