Apogee SE-421 Manuel du propriétaire - Page 17

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TROUBLESHOOTING AND CUSTOMER SUPPORT

Independent Verification of Functionality

If the sensor does not communicate with the datalogger, use an ammeter to check the current draw. It should be

near 1.4 mA when the sensor is not communicating and spike to approximately 1.8 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.

An example datalogger program for Campbell Scientific dataloggers can be found on the Apogee webpage at

https://www.apogeeinstruments.com/downloads/#datalogger.

Zero Offset Error

With the use of certain dataloggers it is possible to measure a non-zero voltage (zero offset) when the sensor

output should be zero (no UV irradiance incident on diffuser). This offset can be corrected by adding or subtracting

the measured offset from the sensor output. However, if the offset is substantial, and your sensor is outputting

unrealistic values then it may need to be recalibrated. In this case, contact Apogee customer support to recalibrate

the sensor.

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

weatherproof-cable-splice/).

Unit Conversion

SU-200 series UV-A sensors are calibrated in energy flux units of W m

value to photon flux units of µmol m

flux units to photon flux.

1) Calculate the sensor output in units of J m

2) Multiply the energy flux units by the conversion factor. It's important to note that each light source needs

a specific conversion factor. The conversion factor used in the example equation is the sunlight

conversion factor.s

(http://www.apogeeinstruments.com/how-to-make-a-

-2

-1

using a conversion factor. Below is an example of how to convert energy

-2

-1

−2

6 ∗ 10

= 60

∗ 0.327

-2

. It is possible to convert the energy flux

= 60

= 19.62