Users Manual

Operating Manual Smart Weather Sensor
92 G. Lufft Mess- und Regeltechnik GmbH, Fellbach, Germany
19.6.2 Command Set
For details of the SDI-12 protocol please refer to the above mentioned standard document.
The commands listed in following table are available for devices of the WS family. The links
in table column „details“ guide you to the description of buffer contents and additional
functions.
The composition of the minimal and the full basic data set depends on the variant (WS100-
UMB ... WS800-UMB) of the device in question (see below). The same applies to the
availability of the additional measurement commands (aM1!, aC1! etc.)
Due the applied measurement processes the devices of the WS family will, different from
other sensors described in the SDI-12 document, in normal operation mode always
measure continuously. This causes some special properties while in this mode:
• The device does not need a “Wakeup” and does not have a sleep mode. So the
reactions to “Break” signals and any related timings are inapplicable. “Break” will be
ignored by WS devices.
• Data requested with M- or C- commands are always available immediately. The
device will always respond with a000n resp. a000nn. This means the device will not
send any service request and will ignore measurement abort signals. The logger
should request the data immediately.
• M- and C- command only differ in the number of values made available in the buffers
(in both cases the maximum permitted by the standards of 9 resp. 20).
• We recommend to use the commands for continuous measurement (R-commands)
to request the data.
• When in power saving mode 2 the device will wake up by a „Break“ signal. Other
functions of the „Break“ signal are not implemented.
• When in power saving mode 2 the device responds to M or C commands with
a002n resp. a002nn and holds the data available within 2 seconds. It will not send a
service request, signals to abort the measurement are ignored.
• For the reduced data set in power saving mode 2 a unified data buffer structure for
all device models has been defined. Depending on the individual model unused
channels will be set to the “invalid” marker 999.9.
Command
Function
Details
?!
Address search (Wildcard request, one device only on bus!)
Standard
a!
Request device active?
Standard
aI!
Request device identification
all
aAb!
Address change to b ( 0 … 9, A …Z, a … z)
Standard
aM!
Measurement basic minimal data set
WS 600/700/800, 500, 400,
300, 200, 100, 501-510, 301-
310, 601, 401, PSM 2 all
aM1!
Measurement temperatures
all
aM2!
Measurement humidity
all
aM3!
Measurement air pressure
all
aM4!
Measurement wind
all
aM5!
Measurement compass
all
aM6!
Measurement precipitation
all
aM7!
Measurement global radiation
all
aM8!
Measurement external temperature
all
aMC!
Measurement, basic minimal data set, transmit values with CRC
see aM!
aMC1! ...
aMC8!
Measurement (assignment of values as for aMn! commands),
transmit values with CRC
see aM1! … aM8!
aC!
Concurrent measurement, full basic data set
see aM1!