Apogee Instruments SQ-642 Owner's Manual - Page 11
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Sensor Calibration
Apogee SQ-640 Quantum Light Pollution Sensors have standard calibration factors of exactly:
Multiply the calibration factor by the measured mV signal to convert sensor output to photon flux density in units
of µmol m
-2
s
-1
:
Calibration Factor (1 µmol m
1
LED Output
-2
(50 µmol m
1 µmol m
-2
-1
s
per mV) * Sensor Output Signal (mV) = Photon Flux Density (µmol m
*
-1
s
)
Sensor Output
50 mV
-2
-1
s
per mV
50
=
50
Example of photon flux density measurement with an
Apogee model SQ-640 Quantum Light Pollution Sensor.
The LED in this example Full yields a photon flux density on
a horizontal plane of 50 µmol m
signal of 50 mV. This signal is converted to photon flux
density by multiplying by the calibration factor of 1 mol
-2
-1
m
s
/ mV.
-2
-1
s
)
-2
-1
s
. This yields an output