Apogee SQ Series Benutzerhandbuch - Seite 17

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TROUBLESHOOTING AND CUSTOMER SUPPORT

Independent Verification of Functionality
Apogee SQ-100X series quantum sensors are self-powered devices and output a voltage signal proportional to
incident PPFD. A quick and easy check of sensor functionality can be determined using a voltmeter with millivolt
resolution. Connect the positive lead wire from the voltmeter to the white wire from the sensor and the negative
(or common) lead wire from the voltmeter to the black 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.
Compatible Measurement Devices (Dataloggers/Controllers/Meters)
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SQ-100X series quantum sensors are calibrated with a standard calibration factor of 10.0 µmol m
s
per mV,
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yielding a sensitivity of 0.1 mV per µmol m
s
. Thus, a compatible measurement device (e.g., datalogger or
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controller) should have resolution of at least 0.1 mV in order to provide PPFD resolution of 1 µmol m
s
.
An example datalogger program for Campbell Scientific dataloggers can be found on the Apogee webpage at
http://www.apogeeinstruments.com/content/Quantum-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:
(http://www.apogeeinstruments.com/how-to-make-a-weatherproof-cable-splice/).
Unit Conversion Charts
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Apogee SQ-100X series quantum sensors are calibrated to measure PPFD in units of µmol m
s
. Units other than
photon flux density (e.g., energy flux density, illuminance) may be required for certain applications. It is possible to
convert the PPFD value from a quantum sensor to other units, but it requires spectral output of the radiation
source of interest. Conversion factors for common radiation sources can be found on the Unit Conversions page in
the Support Center on the Apogee website (http://www.apogeeinstruments.com/unit-conversions/; scroll down to
Quantum Sensors section). A spreadsheet to convert PPFD to energy flux density or illuminance is also provided on
the Unit Conversions page in the Support Center on the Apogee website
(http://www.apogeeinstruments.com/content/PPFD-to-Illuminance-Calculator.xls).