12.4 SDI-12
12.4.1 What is SDI-12?
SDI-12 (Serial Data Interface at 1200 Baud) is a serial data communication standard for interfacing
multiple sensors with a single data recorder. For a detailed description on SDI-12 communication
please refer to
.
12.4.2 What can I do with it?
The USH-9 listens to standard SDI-12 commands as listed in the SDI-12 specifications of version 1.3,
e.g., to trigger a measurement or retrieve measurement results. Additionally, a set of extended SDI-
12 commands is implemented in all SOMMER sensors for instrument configuration.
12.4.3 Configuration
The USH-9 has SDI-12 communication enabled by default. When setting up a SDI-12 network take the
following considerations into account:
n
Each device in the SDI-12 network must have a unique address, e.g. data logger address
0
,
USH-9 address
1
.
n
If the USH-9 operates in polling mode (
set to
SDI-12/RS-485
), meas-
urements are triggered by
M!
commands and data are retrieved by
D!
commands.
n
If the USH- 9 operates in pushing mode (
set to
interval
), data are
retrieved by the
R!
commands.
n
When multiple sensors are connected to the same network, data acquisition should be done in
sequence, i.e., data should have been received from the first sensor before triggering the meas-
urement of the second sensor.
n
Most data loggers control the timing of messages (marking and spacing) automatically. If this is
not the case, please refer to
.
12.4.4 Data structure
The answer from the SDI-12 device is a string containing the sensor address, the requested data and
a terminating carriage return/line feed.
In a string containing measurement data, the measurements are returned in the same order as listed
by the index in
.
1
2
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Manual
