Sdi-12 Communication; Sdi-12 Commands; Sdi-12 Sensor Bus - Decagon Devices VP-3 Operating Manual

SDI-12 Communication

The VP-3 can also communicate using SDI-12 protocol, a three-
wire interface where all sensors are powered (white wire),
grounded (bare wire), and communicate (red wire) on shared
nodes (for more information on the SDI-12 protocol, visit
www.sdi-12.org). Below is a brief description of SDI-12 for
communication. If you plan on using SDI-12 for communication
with the VP-3 Sensor, please see our integrator's guide at
www.decagon.com/support/literature for detailed instructions.

SDI-12 Commands

Following are SDI-12 commands that the VP-3 Sensor responds
to. The sensor address is shown as 'a'. If a '?' is substituted for 'a'
all addresses respond.
Send Identification
Change Address
Address Query
Start Measurement
Send Data

SDI-12 Sensor Bus

Up to 62 sensors can be connected to the same 12 V supply and
communication port on a datalogger. This simplifies wiring
because no multiplexer is necessary. However, one sensor
problem can bring down the entire array (through a short circuit
aI! a13DECAGON VP-3 350<CR><LF>
aAb! b<CR><LF> (b is new address)
?! a<CR><LF>
aM! a0013<CR><LF>
aD0! a+1.17+21.5+0.456<CR><LF> (3 values)
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VP-3 User's Manual
5. Communication