Apogee Instruments S2-412 Owner's Manual - 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

Watts m⁻²

-1

(irradiance) or 0

(radiance). When illuminated, the sensors should return positive values, with

Watts m⁻²

-1

irradiance near 1

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/.