Apogee Instruments S2-411 Manuel du propriétaire - Page 18
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TROUBLESHOOTING AND CUSTOMER SUPPORT
Independent Verification of Functionality
The simplest way to check sensor functionality is the aM2! command. This command returns calibrated outputs
from each detector. Detector temperature should read very near room temperature. When the diffuser or
-1
aperture of the sensor is covered (no incident radiation), the outputs should read very near 0
nm
Watts m⁻²
-1
-1
(irradiance) or 0
nm
sr
(radiance). When illuminated, the sensors should return positive values, with
Watts m⁻²
-1
irradiance near 1
nm
for sunlight on a clear day.
Watts m⁻²
If the sensor does not communicate with the datalogger, use an ammeter to check the current draw. It should be
near 1.5 mA when the sensor is not communicating and spike to approximately 2 mA when the sensor is
communicating. Any current draw greater than approximately 6 mA indicates a problem with power supply to the
sensors, wiring of the sensor, or sensor electronics.
Compatible Measurement Devices (Dataloggers/Controllers/Meters)
Any datalogger or meter with SDI-12 functionality that includes the M or C command.
Example datalogger programs for Campbell Scientific dataloggers can be found on the Apogee webpage at:
https://www.apogeeinstruments.com/content/NDVI-Digital.CR1
Modifying Cable Length
SDI-12 protocol limits cable length to 60 meters. For multiple sensors connected to the same data line, the
maximum is 600 meters of total cable (e.g., ten sensors with 60 meters of cable per sensor). See Apogee webpage
for details on how to extend sensor cable length at
https://www.apogeeinstruments.com/how-to-make-a-
weatherproof-cable-splice/.