Apogee Instruments PYRANOMETER SP-421 소유자 매뉴얼 - 페이지 8

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Cosine Response

Directional, or cosine, response is defined as

the measurement error at a specific angle of

radiation incidence. Error for Apogee silicon-

cell pyranometers is approximately ± 2 % and

± 5 % at solar zenith angles of 45° and 75°,

respectively.

Mean cosine response of eleven Apogee silicon-

cell pyranometers (error bars represent two

standard deviations above and below mean).

Cosine response measurements were made

during broadband outdoor radiometer

calibrations (BORCAL) performed during two

different years at the National Renewable Energy

Laboratory (NREL) in Golden, Colorado. Cosine

response was calculated as the relative difference

of pyranometer sensitivity at each solar zenith

angle to sensitivity at 45° solar zenith angle. The

blue symbols are AM measurements, the red

symbols are PM measurements.