Xylem H-339 - Manual (Page 15)

H-339
SDI-12 Command and Response Protocol 2-3
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 logger may wake the sensor with a break and collect the data anytime after the specified
processing time has elapsed.