Xylem H-424MS V1.1 - Manual (Page 14)

Example of a H-424MS "aM!" command:
Command Response Time Values Description
------------- --------------------- ------- -------- -------------------------------
"aM!" "a0161" 16 sec 1 Wakeup the remote stations
Subsequent Command Response
--------------------------- ------------------------------------
"aD0" a+1
Where:
1 = Fixed dummy “data”.
2.2 Measure Command
The H-424MS Measure Command causes the H-424MS to wake the remote site(s) from low
power sleep. The time required to complete this process is the Wake Interval setting plus 1-
second. During this period the H-424MS transmits wakeup nulls which are detected by the
remote site(s) when they periodically wake and check for activity. To be SDI-12 compliant a
dummy data value is 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
------------------ ---------------------- ------------------------------------
"aM!" "atttn" Initiate measurement
Where:
a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").
M 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.
n is a single digit integer (0-9) 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.
Upon completion of the measurement, a service request "a" is sent to the data recorder
indicating the sensor data is ready. The data recorder may wake the sensor with a break and
collect the data anytime after the service request is received or the specified processing time has
elapsed.
2-2 SDI-12 Command and Response Protocol
H-424MS