Pyranometer Facts

Pyranometer Facts
A pyranometer is a tool used to measure solar irradiance on the surface of the earth. In simple terms a pyranometer measures the amount of sunlight reaching the earth's horizontal plane. The pyranometer was invented by a Swedish meteorologist and physicist names Anders Knutsson Angstrom in 1893. His pyranometer was the first device invented that was able to measure both indirect and direct solar radiation. The main types of pyranometers are thermopile pyranometers, photodiode-based pyranometers, and photovoltaic pyranometers. These three types of pyranometers are classified into either thermopile technology or silicon semiconductor technology.
Interesting Pyranometer Facts:
The spectral response (light sensitivity) of a pyranometer depends on the type of pyranometer.
Thermopile technology is able to convert thermal energy into electrical energy based on temperature difference. Thermopile pyranometers measure the flux density of solar radiation from a 180 degree angle of view. The temperature of the sun exposed area and shadow area are used to determine solar irradiance.
A thermopile pyranometer has a sensor covered in a black coating that absorbs the solar radiation and a glass dome that limits the spectral response (light sensitivity).
In a thermopile pyranometer the active junctions are located under the black coated sensor and radiation absorbed by the black coating heats the junctions.
In a thermopile pyranometer the passive junctions are located in an area protected from solar radiation.
The temperature difference between the active and passive junctions generates a small electrical voltage to provide the solar irradiance measurement.
Thermopile pyranometer technology is useful in a number of professional fields including climatology, research into climate change, photovoltaic systems, the physics of building engineering, and meteorology.
Thermopile pyranometers are most often installed in meteorological stations horizontally.
When a thermopile pyranometer is mounted at the side of a solar panel it is usually mounted with the black sensor on the solar panel plane.
Photodiode-based pyranometers are equipped with a photodiode that is capable of converting the solar spectrum frequency into high speed current. As the temperature rises the current produced also rises.
Photodiode-based pyranometers are equipped with a photodiode, optical filters or diffuser, and a housing dome. The photodiode is the sensor; and the current it produces is in proportion to the irradiance.
Photodiode-based pyranometers are used for lighting and cinema techniques, and in photography.
Photovoltaic pyranometers are equipped with a metallic container, a photovoltaic cell and signal conditioning electronics.
Photovoltaic pyranometers are useful when combined with photovoltaic systems and for diagnosing their malfunctions. They are also used in solar simulators.
Manufacturers of thermopile pyranometers should follow the ISO 9060 standard which the World Meteorological Organization has adopted as standard. The best standard is labeled as secondary standard, while second is labeled as first class and third is labeled as second class.
Pyranometers must be calibrated and calibration standards are determined by the type of pyranometer. Calibration of these tools is dependent on the intended use as well.
The thermopile pyranometers are much more expensive than photovoltaic pyranometers.
The less expensive pyranometers can be useful in farming and monitoring of the environment when absolute accuracy is not required.

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