Xylem H-3311 - Manual (Page 15)

The “Concurrent Measure with CRC” command causes a measurement sequence to be performed
with a CRC appended to the data. Data values generated in response to this command are stored
in the sensor’s buffer for subsequent collection using “D” commands. The data will be retained in
the sensor until another “M”, “C” or “V” command is executed.
Command Response Description
“aCC!” “atttnn” Initiate measurement
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SDI-12 Command & Response Protocol
A “Concurrent Measurement” is one which occurs while other SDI-12 sensors on the bus are also
taking measurements. This command is similar to the “aM!” command, however, the nn field has
an extra digit and the sensor does not issue a service request when it has completed the measurement.
Communicating with other sensors will NOT abort a concurrent measurement. Data values generated
in response to this command are stored in the sensor’s buffer for subsequent collection using “D”
commands. The data will be retained in the sensor until another “M”, “C” or “V” command is executed.
Command Response Description
“aC!” “atttnn” Initiate measurement
Where:
a is the sensor address (“0-9”, “A-Z”, “a-z”, “*”, “?”).
C is an upper-case ASCII character
ttt is a three digit integer (000-999) specifying the maximum time, in seconds, the sensor
will take to complete the command and have measurement data available in its buffer.
nn is a two digit integer (00-99) specifying the number of values that will be placed in the
data buffer. If “n” is zero (0), no data will be available using subsequent “D” commands.
The data recorder may wake the sensor with a break and collect the data anytime after the specified
processing time has elapsed.
Concurrent Measurement Command
Concurrent Measurement Command with CRC
example of an ‘am!’ Command:
Command Response Time Values Description
‘aMC!’ “a0012” 1 sec 2 Return encoder position
Subsequent Command Response
“aD0” a+X.XX+NNNN
Where:
X.XX = Current position (stage), in user programmable units
NNNN = Current position, in raw position counts
YYY = CRC (ASCII Characters)