Apogee SQ-225 Benutzerhandbuch - Seite 16

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TROUBLESHOOTING AND CUSTOMER SUPPORT

Independent Verification of Functionality

Apogee SQ-200 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)

SQ-200 series quantum sensors are calibrated with a standard calibration factor of 1.0 µmol m

-2

-1

per mV (SQ-212 and SQ-

222) or 0.5 µmol m

per mV (SQ-215 and SQ-225), yielding a sensitivity of 1 mV per µmol m

(SQ-212 and SQ-222) or 2

-2

-1

-2

-1

mV per µmol m

-2

-1

(SQ-215 and SQ-225). Thus, a compatible measurement device (e.g., datalogger or controller) should have

resolution of at least 1 mV in order to provide PPFD resolution of 1 µmol m

-2

-1

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 PPFD in units of µmol m

. Units other than photon flux

-2

-1

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).

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