Apogee SQ-204X-SS Owner's Manual - Page 12
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Sensor Calibration
Apogee SQ-204X models have a standard PPFD calibration factor of exactly:
Multiply this calibration factor by the difference of the measured mA signal and the 4.0 mA offset to convert
sensor output to PPFD in units of µmol m
Calibration Factor (250 µmol m
250
Full Sunlight
(2000 µmol m
-2
-1
250.0 µmol m
s
per mA with a 4 mA offset
-2
-1
s
:
-2
-1
s
per mA) * [Sensor Output Signal (mA) – Offset (4.0 mA)] = PPFD (µmol m
*
(12.0
-2
s
-1
)
Sensor Output
12.0 mA
–
4)
=
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
output signal of 12.0 mA. The signal is converted to
PPFD by subtracting the 4.0 mA offset and then
multiplying by the calibration factor of 250 µmol m
-1
s
per mA.
-2
s
2000
-2
-1
s
. This yields an
-2
-1
)