Apogee Instruments SQ-100X Series Manuale d'uso - Pagina 18

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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

per mV,

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yielding a sensitivity of 0.1 mV per µmol m

. 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

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

. 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).