Xylem H-3551 - Manual (Page 24)

5-6 SDI-12 Command and Response Protocol
H-3551
5.4 Send Data Command
The Send Data command returns sensor data generated as the result of previous "aM!", "aM1!",
"aM2!", "aC!", "aC1!", "aC2!" or "aV!" commands. Values returned will be sent in 33 characters
or less. The sensor's data buffer will not be altered by this command.
Command Response
"aD0!" "apd.d"
Where:
a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").
D0 are upper-case ASCII characters.
p Is a polarity sign (+ or -)
d.d represents numeric digits before and/or after the decimal. A decimal may be used in
any position in the value after the polarity sign. If a decimal is not used, it will be
assumed to be after the last digit.
For example: +3.29 +23.5 -25.45 +300
If the "aD0!" returns no data (“a” only), it means that no measurement data is available
(or the measurement was aborted) and a new "M" command must be sent.
Example of a H-3551 "aD0!" command:
Previous Command
Response
"aM!" "a2721"
Subsequent Command Response Description
"aD0" a+0 Purge failed (low battery)
"aD0" a+1 Purge succeeded