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16
CHAPTER 3
Performing Advanced Functions
GND
SDI−Sense
SDI−POWER
Figure 10. The SDI-12 Connector
If you do not use an SDI-12 sensor with the proper cable already
mounted, but will connect it to the SDI bus through a wiring box, it
is absolutely crucial to obey the following instructions: first identify
the function of each of the sensors cables. Then connect them to
the wiring box in exactly the folloing order: First connect SDI-GND.
Then connect SDI-POWER (only if a sensor receives its power sup-
ply from the RTU) and last connect SDI-DATA. Else you might
cause the SDI-12 bus to perform unexpectedly!
CAUTION
Some SDI-12 sensors have a rather high startup current,
which prevents operation with our low power addSDI RTU. Always
check your SDI-12 sensor's peak current draw upon start-up! This is
of particular importance when connecting more than one sensor to
the SDI-12 bus - while one sensor might still operate flawlessly with
your RTU, two might draw too much current and cause the RTU to
shut off the bus. This will occurr when the total power draw on the
SDI-12 bus goes beyond 500mA. In case of doubt or questions
please consult your sensor supplier or your Adcon dealer.
Note: Please see also SDI-12 spec for additional wiring and setup
information.
To enable the SDI-12 bus operation, a jumper must be installed
between GND (Pin 1) and SDI-Sense (Pin 2). This jumper is factory
installed in the connector of the standard 1m cable, which comes
with your addSDI RTU.
Note: When the SDI-12 bus is not used, please disconnect the SDI
connector and the solar panel from your addSDI. The RTU
will then switch to a power save mode.
SDI−GND
gray
1
5
2
4
3
SDI−DATA
yellow
green
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