characters of data in response to a
D
command that follows an
M!
or
MC!
command. A sensor
may return up to 75 characters of data in response to a
D
command that follows a
C!
or
CC!
command. Data values are separated by plus or minus signs.
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!
.
B.1.11 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.
B.1.12 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.
B.2 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.
SN500SS Net Radiometer
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