Sensor Calibration
Apogee amplified full-spectrum quantum sensors, models SQ-212 and SQ-215, have a standard PPFD calibration
factor of exactly:
SQ-512: 1.6 µmol m
-2
s
-1
per mV
SQ-515: 0.8 µmol m
-2
s
-1
per mV
Multiply this calibration factor by the measured voltage to convert sensor output to PPFD in units of µmol m
-2
s
-1
:
Calibration Factor (0.8 µmol m
-2
s
-1
per mV) * Sensor Output Signal (mV) = PPFD (µmol m
-2
s
-1
)
0.8 * 2500 = 2000
Example of PPFD measurement with an Apogee quantum
sensor. Full sunlight yields a PPFD on a horizontal plane at
the Earth’s surface of approximately 2000 µmol m
-2
s
-1
. This
yields an output signal of 2500 mV for the 0-5 V option or
an output signal of 1250 mV for the 0-2.5 V option. The
signal is converted to PPFD by multiplying by the
calibration factor.
Full Sunlight
(2000 µmol m
-2
s
-1
)
SQ-512
SQ-515
Sensor Output: 1250 mV
Conversion Factor: 1.6 µmol m
-2
s
-1
per mV
Sensor Output: 2500 mV
Conversion Factor: 0.8 µmol m
-2
s
-1
per mV