may return up to 75 characters of data in response to a
D
command that follows a
C!
or
CC!
command.
Command:
aD0!
(
aD1!
…
aD9!
)
Response:
a<values><CR><LF>
or
a<values><CRC><CR><LF>
where:
a
= the sensor address
<values>
= values returned with a polarity sign (+ or –)
<CR><LF>
= terminates the response
<CRC>
= 16-bit CRC code appended if data was requested with a
MC!
or
aCC!
.
C.2.11 Continuous measurement command (aR0! … aR9!)
Sensors that are able to continuously monitor the phenomena to be measured can be read
directly with the
R
commands (
R0!
…
R9!
). The response to the
R
commands mirrors the Send
Data command (
aD0!
). A maximum of 75 characters can be returned in the
<values>
part of the
response to the
R
command.
C.2.12 Extended commands
Many sensors support extended SDI-12 commands. An extended command is specific to a make
of sensor and tells the sensor to perform a specific task. They have the following structure.
Responses vary from unit to unit. See the sensor manual for specifics.
Command:
aXNNNN!
The command will start with the sensor address (a), followed by an X, then a set of optional
letters, and terminate with an exclamation point.
Response:
a<optional values><CR><LF>
The response will start with the sensor address and end with a carriage return/line feed.
C.3 SDI-12 transparent mode
System operators can manually interrogate and enter settings in probes using transparent mode.
Transparent mode is useful in troubleshooting SDI-12 systems because it allows direct
communication with probes. Data logger security may need to be unlocked before activating the
transparent mode.
Transparent mode is entered while the PC is communicating with the data logger through a
terminal emulator program. It is accessed through Campbell Scientific data logger support
SDMS40 Multipoint Scanning Snowfall Sensor
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