Apogee Instruments SQ-647 Benutzerhandbuch - Seite 14
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Low Light Measurements
Accurate low light measurements are required in flowering and light pollution studies. Research indicates
flowering can be triggered in some plants at photosynthetic and/or far red photon flux densities less than 0.1 mol
-2
-1
m
s
. The threshold photon flux density at which flowering is triggered is variable among species. Two of the
most light sensitive species are Poinsettias and Cannabis. For reference, photon flux density of moonlight when the
moon is full and near the minimum zenith angle is 0.005 mol m
-2
-1
s
.
The model SQ-620 Extended Range Quantum Sensor can measure a photon flux density range of 0-4000 mol m
-2
-1
s
. The model SQ-640 Quantum Light Pollution Sensor is designed for low light measurements and can only
measure a photon flux density range of 0-200 mol m
(the sensor will output values beyond, 200 mol m
-2
-1
-2
-1
s
s
,
but these are beyond the linear range of the sensor), and is referred to as the low light version. The sensitivity of
the SQ-640 is twenty times higher than the sensitivity of the SQ-620 (1 mV per mol m
-2
-1
s
versus 0.05 mV per
mol m
-2
-1
s
) to provide greater measurement resolution under low light conditions. For example, if the photon
flux density were 0.1 mol m
-2
-1
s
, the SQ-640 would output 0.1 mV, whereas the SQ-620 would output 0.005 mV.