Apogee Instruments SP-230-SS Manuale d'uso - Pagina 14

Sfoglia online o scarica il pdf Manuale d'uso per Strumenti di misura Apogee Instruments SP-230-SS. Apogee Instruments SP-230-SS 20. Pyranometer

Silicon-cell pyranometers can still be used to measure shortwave radiation in conditions other than clear sky or

from radiation sources other than incoming sunlight, but spectral errors occur when measuring radiation with

silicon-cell pyranometers in these conditions. The graphs below show spectral error estimates for Apogee silicon-

cell pyranometers at varying solar zenith angles and varying atmospheric air mass. The diffuser is optimized to

minimize directional errors, thus the cosine response graph in the Specifications section shows the actual

directional errors in practice (which includes contributions from the spectral shift that occurs as solar zenith angle

and atmospheric air mass change with time of day and time of year). The table below provides spectral error

estimates for shortwave radiation measurements from shortwave radiation sources other than clear sky solar

radiation.

Spectral response of Apogee SP series

pyranometers compared to solar

radiation spectrum at Earth's surface.

Silicon-cell pyranometers, such as

Apogee SP series, are only sensitive to

the wavelength range of

approximately 350-1100 nm, and are

not equally sensitive to all

wavelengths within this range. As a

result, when the spectral content of

solar radiation is significantly different

than the spectrum that silicon-cell

pyranometers were calibrated to,

spectral errors result.

Spectral error for Apogee SP series

pyranometers as a function of solar

zenith angle, assuming calibration at

a zenith angle of 45°.