LPPYRA02
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V2.6
2
WORKING PRINCIPLE
LPPYRA02 pyranometer is based on a thermopile sensor. The thermopile sensitive sur-
face is coated with a black matt paint, which allows the pyranometer not to be selec-
tive at different wavelengths. The pyranometer spectral range is determined by the
transmission of the two glass domes type K5.
Radiant energy is absorbed by the thermopile black surface, thus creating a difference
of temperature between the center of the thermopile (hot junction) and the pyranom-
eter body (cold junction). Thanks to the Seebeck effect, the difference of temperature
between hot and cold junction is converted into a Difference of Potential.
In order to grant the thermopile a proper thermal insulation from the wind and reduce
the sensitivity to thermal irradiance, LPPYRA02 is equipped with two concentric domes
having 50 mm and 32 mm outer diameter. The domes protect the thermopile from the
dust, which might change spectral sensitivity if it lies on the black surface.
To prevent internal condensation forming on the internal side of the dome under cer-
tain climatic conditions, silica gel tablets are inserted inside the pyranometer to ab-
sorb humidity.
Fig. 2.1: scheme of principle LPPYRA02 (version with mV output)
Thermopile
Surge
Protector
Connector pins
Housing
To cable shield
