Apogee Instruments SP-110 Manual del usuario - Página 18
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TROUBLESHOOTING AND CUSTOMER SUPPORT
Independent Verification of Functionality
Apogee models SP-110 and SP-230 pyranometers are self-powered devices and output a voltage signal
proportional to incident shortwave radiation. A quick and easy check of sensor functionality can be determined
using a voltmeter with millivolt (mV) 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 diffuser 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.
The heaters inside Apogee model SP-230 are designed to mitigate effects from snow, frost, and dew by warming
the sensor body temperature approximately 3 C above ambient air temperature, while under conditions of no
solar loading or radiant heating. A quick and easy check of heater functionality can be accomplished with an
ohmmeter. Connect the lead wires of the ohmmeter to the yellow and blue wires from the sensor. The resistance
should read approximately 780 Ω ± 1%.
Compatible Measurement Devices (Dataloggers/Controllers/Meters)
-2
Models SP-110 and SP-230 pyranometers are calibrated with a standard calibration factor of 5.0 W m
per mV,
-2
yielding a sensitivity of 0.2 mV per W m
. Thus, a compatible measurement device (e.g., datalogger or controller)
-2
should have resolution of at least 0.2 mV, in order to provide shortwave radiation resolution of 1 W m
.
An example datalogger program for Campbell Scientific dataloggers can be found on the Apogee webpage at
http://www.apogeeinstruments.com/content/Pyranometer-Unamplified.CR1.
Effect of 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 1 mega-ohm or higher then there is negligible effect on the
pyranometer calibration, even after adding up to 100 m of cable. Apogee model SP series pyranometers use
shielded, twisted pair cable, which minimizes electromagnetic interference. This is particularly important for 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/).