Apogee Instruments SP-230 Gebruikershandleiding - Pagina 16
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16
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 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 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 white and green 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
-2
mV, yielding a sensitivity of 0.2 mV per W m
. Thus, a compatible measurement device (e.g., datalogger
or controller) should have resolution of at least 0.2 mV, in order to provide shortwave radiation resolution
of 1 W m
-2
.
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/).