Connecting to loggers or controllers
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17
GP2 wiring using external power
The WET150 is a highly energy efficient sensor. Depending upon the
measurement frequency and the number of WET150 sensors in the
network, the internal GP2 logger/controller batteries are capable of
providing power for many tens of thousands of sensor readings over periods
longer than a year.
If the WET150 is used in conjunction with other more power-hungry SDI-12
sensors, it may be desirable to use a larger external power supply for the
SDI-12 network. The functioning of the GP2 logger/controller itself can
remain running on its own internal batteries independently of an external
power source for the SDI-12 network.
To use an external power supply for the SDI-12 network, do not connect
anything to the GP2’s “+12 0.5A” power terminal. Instead wire the SDI-12
network power (white wire on cable type
“SMSC/lw-05”) to the external
power 12Vdc terminal.
Wiring connection
diagram showing
external SDI-12 power
connections for the SDI-
12 network, along with
the optional green screen
wire
Ensure there is a fuse or other protection in-line with this external power
source in case short-circuit faults develop on the SDI-12 network.
The Ground or 0V terminal of the external power source should be wired into
the GND terminal on the GP2, along with the Ground wire of the SDI-12
network (blue wire on cable type “SMSC/lw-05”).
In the external power supply configuration shown above, power is
permanently applied to the SDI-12 network. This may not be the most
desirable or efficient way to run the network. An alternative would be to wire
one of the GP2 internal relays in series with the external power supply and
the SDI-12 network power wire.
The GP2 logger/controller program can then be configured to switch in the
power only when taking measurements for greater external power efficiency.
e.g In DeltaLINK program’s
Measurement
,
Power channel
select RLY1.
