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A typical pyranometer does not require any power to operate.
Additional recommended knowledge
The name pyranometer stems from Greek, "pyr" meaning "fire" and "ano" meaning "sky".
The solar radiation spectrum extends approximately from 300 to 2800 nm. Pyranometers usually cover that spectrum with a spectral sensitivity that is as “flat” as possible.
For a flux density or irradiance measurement it is required by definition that the response to “beam” radiation varies with the cosine of the angle of incidence; i.e. full response at when the solar radiation hits the sensor perpendicularly (normal to the surface, sun at zenith, 0 degrees angle of incidence), zero response when the sun is at the horizon (90 degrees angle of incidence, 90 degrees zenith angle), and 0.5 at 60 degrees angle of incidence. It follows from the definition that a pyranometer should have a so-called “directional response” or “cosine response” that is close to the ideal cosine characteristic.
Design of pyranometers
In order to attain the proper directional and spectral characteristics, a pyranometer’s main components are:
The black coating on the thermopile sensor absorbs the solar radiation. This radiation is converted to heat. The heat flows through the sensor to the pyranometer housing. The thermopile sensor generates a voltage output signal that is proportional to the solar radiation.
Pyranometers are frequently used in meteorology, climatology, solar energy studies and building physics. They can be seen in many meteorological stations - typically installed horizontally and next to solar panels - typically mounted with the sensor surface in the plane of the panel.
Pyranometers are standardised according to the ISO 9060 standard, that is also adopted by the World Meteorological Organisation (WMO). This standard discriminates three classes. The best is (confusingly) called "secondary standard", the second best "first class" and the last one "second class".
Calibration is typically done relative to World Radiometric Reference (WRR). This reference is maintained by PMOD in Davos, Switzerland
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Pyranometer". A list of authors is available in Wikipedia.|