Apogee SQ-514 Руководство пользователя - Страница 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

per mA) * Sensor Output Signal (mA) = PPFD (µmol m

-2

-1

)

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

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

. 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

per mA.

-2

-1

-2

-1

)

2000