User Manual

Cosine Response
Mean cosine response of twenty-
three SQ series quantum sensors
(error bars represent two
standard deviations above and
below mean). Cosine response
measurements were made by
direct side-by-side comparison to
the mean of four reference
thermopile pyranometers, with
solar zenith angle-dependent
factors applied to convert total
shortwave radiation to PPFD. Blue
points represent the AM response
and red points represent the PM
response.
Directional, or cosine, response is defined as
the measurement error at a specific angle of
radiation incidence. Error for Apogee SQ
series quantum sensors is approximately ± 2
% and ± 5 % at solar zenith angles of 45° and
75°, respectively.