Apogee S2-442 Panduan Pemilik - Halaman 17

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TROUBLESHOOTING AND CUSTOMER SUPPORT

Independent Verification of Functionality

Apogee S2-141 PAR-FAR sensors are self-powered devices and output two voltages, one proportional to PPFD and

one proportional to far-red photon flux density. A quick and easy check of sensor functionality can be determined

using a voltmeter with millivolt resolution. To check the PAR sensor, connect the positive lead wire from the

voltmeter to the yellow wire from the sensor and the negative (or common) lead wire from the voltmeter to the

blue wire from the sensor. Direct the sensor head toward a light source and verify the sensor provides a signal.

Increase and decrease the distance from the sensor head to the light source to verify that the signal changes

proportionally (decreasing signal with increasing distance and increasing signal with decreasing distance). Blocking

all radiation from the sensor should force the sensor signal to zero. To check the far-red sensor, repeat the process

above by connecting positive lead wire from the voltmeter to the white wire from the sensor and the negative lead

wire from the voltmeter to the black wire from the sensor.

Compatible Measurement Devices (Dataloggers/Controllers/Meters)

Apogee S2-141 PAR-FAR sensors are calibrated with approximate calibration factors of 100 mol m

PPFD measurement and 50 mol m

sensitivities of 0.01 mV per mol m

measurement device (e.g., datalogger or controller) should have voltage measurement resolution of at least 0.01

mV in order to provide PPFD resolution of 1 mol m

resolution of 1 mol m

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An example datalogger program for Campbell Scientific dataloggers can be found on the Apogee webpage

(https://www.apogeeinstruments.com/content/PAR-Far-Sensor-Unamplified.CR1).

Cable Length

When the sensor is connected to a measurement device with high input impedance, sensor output signals are not

changed by shortening the cable or splicing on additional cable in the field. Tests have shown that if the input

impedance of the measurements device is greater than 1 mega-ohm there is negligible effect on the calibration,

even after adding up to 100 m of cable. All Apogee sensors use shielded, twisted pair cable to minimize

electromagnetic interference. For best measurements, the shield wire must be connected to an earth ground. This

is particularly important when using the sensor with long lead lengths in electromagnetically noisy environments.

Modifying Cable Length

See Apogee webpage for details on how to extend sensor cable length

to-make-a-weatherproof-cable-splice/).

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per mV for far-red photon flux density measurement, yielding approximate

and 0.02 mV per mol m

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, respectively. Thus, a compatible

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and 0.02 mV in order to provide far-red photon density

(http://www.apogeeinstruments.com/how-

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per mV for