Xylem H-335 - Manual (Page 18)

2-2 SDI-12 Command and Response Protocol H-335
Example of a H-335 "aM!" command:
Command Response Time Values Description
"aM!" "a0034" 3 sec 4 Make current measurement
Subsequent Command Response
"aD0" a+AA.AA+BB.BB+CC.CC+DD.DD
Where:
AA.AA = Gate Arc Length
BB.BB = Gate Height
CC.CC = User Angle (Degrees)
DD.DD = Sensor Temperature (C)
2.2 Measure Command
The Measure Command causes a measurement sequence to be performed. The H-335 supports three different
measure commands (“aM”, “aM1" and “aM2"). 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
------------------ ---------------------- ------------------------------------
"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.