Apogee SQ-645 Owner's Manual - Page 12

Browse online or download pdf Owner's Manual for Accessories Apogee SQ-645. Apogee SQ-645 16 pages. Quantum light pollution sensor

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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

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. 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

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The model SQ-620 Extended Range Quantum Sensor can measure a photon flux density range of 0-4000 mol m

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. 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

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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

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versus 0.05 mV per

mol m

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) to provide greater measurement resolution under low light conditions. For example, if the photon

flux density were 0.1 mol m

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, the SQ-640 would output 0.1 mV, whereas the SQ-620 would output 0.005 mV.