Apogee SQ-514 Manual del usuario - Página 11
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OPERATION AND MEASUREMENT
Connect the sensor to a measurement device (meter, datalogger, controller) capable of measuring and displaying a
4-20 mA signal. To maximize measurement resolution and signal-to-noise ratio, the input range of the
measurement device should closely match the output range of the quantum sensor. DO NOT connect the sensor
to a power source greater than 24 V DC.
Sensor Calibration
Apogee SQ-514 sensors have a standard PPFD calibration factor of exactly:
Multiply this calibration factor by the measured mA signal to convert to PPFD in units of µmol m
Calibration Factor (250 µmol m
250
Full Sunlight
(2000 µmol m
250.0 µmol m
-2
-1
s
per mA) * Sensor Output Signal (mA) = PPFD (µmol m
*
-2
-1
s
)
Sensor Output
12 mA
White: 4-20 mA signal output
Red: Input power (7-24 V DC)
Black: Ground (for sensor signal and input power)
Clear: Shield/Ground
-2
-1
s
per mA
(12 – 4)
Example of PPFD measurement with an Apogee SQ-514
quantum sensor. Full sunlight yields a PPFD on a horizontal
plane at the Earth's surface of approximately 2000 µmol
-2
-1
m
s
. This yields an output signal of 12 mA. The signal is
converted to PPFD by subtracting the 4.0 mA offset and
then multiplying by the calibration factor of 250 µmol
-2
-1
m
s
per mA.
-2
-1
s
:
-2
-1
s
)
=
2000