Apogee SQX Series Manuel du propriétaire - Page 17
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TROUBLESHOOTING AND CUSTOMER SUPPORT
Independent Verification of Functionality
Apogee SQ-200X series quantum sensors provide an amplified voltage output that is proportional to incident PPFD.
A quick and easy check of sensor functionality can be determined using a DC power supply and a voltmeter. Power
the sensor with a DC voltage by connecting the positive voltage signal to the red wire from the sensor and the
negative (or common) to the black wire from the sensor. Use the voltmeter to measure across the white wire
(output signal) and black wire. 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-200X series quantum sensors are calibrated with a standard calibration factor of 1.6 µmol m
s
per mV (SQ-
-2
-1
-2
-1
212X) or 0.8 µmol m
s
per mV (SQ-215X), yielding a sensitivity of 0.6 mV per µmol m
s
(SQ-212X) or 1.25 mV
-2
-1
per µmol m
s
(SQ-215X). Thus, a compatible measurement device (e.g., datalogger or controller) should have
-2
-1
resolution of at least 0.6 mV to provide PPFD resolution of 1 µmol m
s
.
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 SQX 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 in
the Unit Conversions page in the Support Center on the Apogee website
(http://www.apogeeinstruments.com/content/PPFD-to-Illuminance-Calculator.xls).