Apogee SP-214 Manual del usuario - Página 13
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Sensor Calibration
All Apogee un-amplified pyranometer models have a standard calibration factor of exactly:
Multiply this calibration factor by the measured mV signal to convert sensor output to shortwave radiation in units of W m
Calibration Factor (5.0 W m
5.0
Full Sunlight
(1000 W m
Spectral Errors for Measurements with Silicon-cell Pyranometers
Apogee SP series pyranometers are calibrated under electric lamps in a calibration laboratory. The calibration procedure
simulates calibration under clear sky conditions at a solar zenith angle of approximately 45°. However, due to the limited
spectral sensitivity of silicon-cell pyranometers compared to the solar radiation spectrum (see graph below), spectral errors
occur when measurements are made in conditions that differ from conditions the sensor was calibrated under (e.g., the solar
spectrum differs in clear sky and cloudy conditions, thus measurements in cloudy conditions result in spectral error because
sensors are calibrated in clear sky conditions).
5.0 W m
per mV) * Sensor Output Signal (mV) = Total Shortwave Radiation (W m
-2
*
200
-2
)
Sensor Output
200 mV
-2
per mV
=
1000
Example of total shortwave radiation measurement with
an Apogee SP-110 pyranometer. Full sunlight yields total
shortwave radiation on a horizontal plane at the Earth's
surface of approximately 1000 W m
output signal of 200 mV. The signal is converted to
shortwave radiation by multiplying by the calibration
factor of 5.0 W m
-2
per mV.
13
-2
:
)
-2
-2
. This yields an