Apogee Instruments SP-212 Manuel du propriétaire - Page 4
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Solar radiation at Earth's surface is typically defined as total radiation across a wavelength range of 280 to 4000
nm (shortwave radiation). Total solar radiation, direct beam and diffuse, incident on a horizontal surface is defined
as global shortwave radiation, or shortwave irradiance (incident radiant flux), and is expressed in Watts per square
-2
meter (W m
, equal to Joules per second per square meter).
Pyranometers are sensors that measure global shortwave radiation. Apogee SP series pyranometers are silicon-cell
pyranometers and are only sensitive to a portion of the solar spectrum, approximately 350-1100 nm
(approximately 80 % of total shortwave radiation is within this range). However, silicon-cell pyranometers are
calibrated to estimate total shortwave radiation across the entire solar spectrum. Silicon-cell pyranometer
specifications compare favorably to specifications for World Meteorological Organization (WMO) moderate and
good quality classifications and specifications for International Organization of Standardization (ISO) Class C
classification, but because of limited spectral sensitivity, they do not meet the spectral specification necessary for
WMO certification.
Typical applications of silicon-cell pyranometers include incoming shortwave radiation measurement in
agricultural, ecological, and hydrological weather networks, and solar panel arrays.
Apogee Instruments SP series pyranometers consist of a cast acrylic diffuser (filter), photodiode, and signal
processing circuitry mounted in an anodized aluminum housing, and a cable to connect the sensor to a
measurement device. Sensors are potted solid with no internal air space and are designed for continuous total
shortwave radiation measurement on a planar surface in outdoor environments. SP series sensors output an
analog voltage that is directly proportional to total shortwave radiation from the sun. The voltage signal from the
sensor is directly proportional to radiation incident on a planar surface (does not have to be horizontal), where the
radiation emanates from all angles of a hemisphere.