5
COMMUNICATION
GS3
port on the data logger. This simplifies wiring because no multi-
plexer is necessary. On the negative side, one sensor problem can
bring down the entire array (through a short circuit, etc.). To avoid
this problem, we recommend the user make an independent junction
box with wire harnesses where all sensor wires are connected to wire
lugs so sensors can be disconnected if a problem arises. A single three
wire bundle can be run from the junction box to the data logger.
The SDI-12 protocol requires that all sensors have a unique address.
GS3 sensors come from the factory with an SDI-12 address of 0. To
add more than one SDI-12 sensor to a system, the sensor address
must change. Address options include 0...9, A...Z, a...z. There are
two ways to set the SDI-12 sensor address. The best and easiest is
to use Decagon’s ProCheck (if the option is not available on your
ProCheck, please upgrade to the latest version of firmware).
SDI-12 addressing can be accessed in the “Config” menu by selecting
“SDI-12 Address” and pressing “Enter.” To change the SDI-12 ad-
dress, press the up and down arrows until you see the desired address
and push “Enter.” SDI-12 communication allows many parameters
to be communicated at once, so you can also see things like the sen-
sor model, SDI-12 version, etc. SDI-12 communication is also sup-
ported in Campbell Scientific data loggers like the CR10X, CR1000,
CR3000, etc. Direct SDI-12 communication is supported in the “Ter-
minal Emulator” mode under the “Tools” menu on the “Connect”
screen. Detailed information on setting the address using CSI data
loggers can be found on our website at
http://www.decagon.com/sup
port/downloads/
.
The sensor can be powered using any voltage from 3.6 to 15 VDC,
but 12 V is optimal. The SDI-12 protocol allows the sensors to be
continuously powered, and we recommended that the power (white
wire) be connected to a continuous 12 VDC source. However, the
sensor can also be used with a switched 12 V source. This can help
reduce power use (although the GS3 sensors use very little power,
0.03 mA quiescent)) and will allow the sensor array to be reset if a
problem arises.
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