Apogee SQ-100 Series Manuale d'uso - Pagina 15

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TROUBLESHOOTING AND CUSTOMER SUPPORT

Independent Verification of Functionality:

Apogee SQ-100 and SQ-300 series quantum sensors are self-powered devices and output a voltage

signal proportional to incident PPF. 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 red

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):

SQ-100 and SQ-300 series quantum sensors are calibrated with a standard calibration factor of 5.0 µmol

-2

-1

-2

-1

per mV, yielding a sensitivity of 0.2 mV per µmol m

. Thus, a compatible measurement device

(e.g., datalogger or controller) should have resolution of at least 0.2 mV in order to provide PPF resolution

-2

-1

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:

Apogee SQ series quantum sensors are calibrated to measure PPF in units of µmol m

-2

-1

. It is possible to

convert the PPF value to units of light quantity (e.g., footcandles or lux), but it requires conversion factors

that are specific to the radiation source of interest. These conversion factors can be found in the

Knowledge Base on the Apogee website (http://www.apogeeinstruments.com/knowledge-base/; scroll

down to Quantum Sensors section).