Apogee Instruments SQ-615 Owner's Manual - Page 16
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TROUBLESHOOTING AND CUSTOMER SUPPORT
Independent Verification of Functionality
Apogee SQ-612 and SQ-615 ePAR Sensors provide an amplified voltage output that is proportional to incident
photon flux density for the 400-750 nm wavelength range. 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 (signal output) and black wire (signal ground). 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)
-2
-1
SQ-600 ePAR Sensors are calibrated with a standard calibration factor of 1.6 µmol m
s
per mV (SQ-612) or 0.8
-2
-1
-2
-1
-2
-1
µmol m
s
per mV (SQ-615), yielding a sensitivity of 0.6 mV per µmol m
s
(SQ-612) or 1.3 mV per µmol m
s
(SQ-615). Thus, a compatible measurement device (e.g., datalogger or controller) should have resolution of at least
-2
-1
0.6 mV (SQ-612) or 1.3 mV (SQ-615) in order to provide photon flux density resolution of 1 µmol m
s
.
An example datalogger program for Campbell Scientific dataloggers can be found on the Apogee webpage at
https://www.apogeeinstruments.com/downloads/#datalogger.
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/).