16
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Connecting to loggers or controllers
GP2 wiring using internal power
The GP2 logger controller incorporates a program-controlled power rail
specifically for SDI-12 applications. This 12V supply is generated from the
internal logger battery pack via a voltage step-up circuit and is current
limited in case of faults on the SDI-12 network.
SDI-12 sensors typically require a 3-wire connection: Power, Ground and
Data. This is the case with the WET150 but the cabling system includes
additional wires which are not normally used within an SDI-12 network.
To create an SDI-12 network based upon a GP2 logger controller, use cable
type “SMSC/lw-05” to bring the network connections out of the GP2 case.
This is a shielded 5-way, 5-metre-long cable with bare wires on one end
and a 5-way M12 connector on the other. Use this to connect one WET150
directly to a GP2, or with the addition of other 5-way M12 extension cables
and T-pieces, connect multiple sensors in a network.
** Optional. The green wire is connected to the cable screen. The SDI-12
specification does not require the green wire / cable screen to be
connected. .
If there is a lot of electrical noise in the
environment, connecting the green screen wire to
the GND terminal (with the blue ground wire) in
the GP2 may help reduce data corruption. The
figure on the right illustrates the wire and terminal
connections with the optional green screen wire.
The brown and grey wires in cable type “SMSC/lw-05” are not normally
required for SDI-12 so should be insulated from shorting to any terminals
inside the GP2, or they may be trimmed off. The same applies to the
green screen wire if it is not used.
Power is automatically supplied when the WET150 sensor is selected in
the DeltaLINK program.
Wire colour
GP2 terminal
(SDI-12 block)
SDI-12 function
M12 connector
pin
Brown
Not connected
1
White
+12V 0.5A
Network power
2
Blue
GND
Ground
(for power and data)
3
Black
DATA
Data (send and receive)
4
Grey
Not connected
5
Green
Not connected **
(Cable screen) **
Shell / nut