Xylem H-3342 - Manual (Page 16)

3-4 SDI-12 Command and Response Protocol
H-3342
3.2 Concurrent Measurement Command
This is a new command for the Version 1.2 SDI-12 Specification. 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.