Sunshine duration sensor
The Sunshine Duration sensor PCTEL004 measures sunshine status and duration. The WMO (World Meteorological Organization) defines the sunshine duration as the time during which the direct solar radiation exceeds the level of 120 W/m² .
The PCTEL004 performs the measure of radiation with an array of photodiodes arranged in a particular geometry which allows to obtain an accurate measurement in any weather conditions. This solution avoids the use of mechanical moving parts and ensures high reliability over time. The instrument, besides indicating the presence of sun as required by the WMO, measures also direct radiation (SRD), therefore it can be used as a low cost alternative to a pyrheliometer, which use is bound to a solar tracker.
The PCTEL004 is equipped with a separately heating element powered and galvanically isolated, which prevents the formation of condensation on the glass surface onto which the sensitive elements are placed. For harsh climates, the abovementioned versions are available with a second heating element (option R), which prevents the formation of ice and prevents snow from settling. The instrument does not need any positioning adjustment during the year and it can be installed on a mast or on a proper fixing base (optional). The application fields are multiple: from the agronomy (agricultural science) to the study the growth of crops, to photovoltaic systems for verifying their performance, to building automations for automatic opening/closing of blinds, shutters and, in general, to all those areas where it is necessary to monitor the presence of sunlight.
Operating Principle: The Sunshine Duration PCTEL004 is based on the use of 16 sensors arranged in such a way that, in the presence of sun, at least one of the photo-detectors is exposed to sun light directly from the sun (besides the diffusion component). Those sensors which are not directly illuminated by the sun are used for the measurement of the diffused light that is subtracted from the measurement of the sensor which sees the sun directly, to get direct radiation. The cylindrical glass protects the sensors and the internal circuits of the instrument from the weather and at the same time provides an excellent transparency to sunlight. In order to avoid the formation of condensation inside the instrument, in addition to the heating element, the PCTEL004 is supplied with a cartridge that must be loaded with desiccant material in colloidal silica (Silica-gel).