Xylem H-4161 - Manual (Page 19)

H-4161
SDI-12 Command and Response Protocol 3-3
3.2 Measure Command
The H-4161 is not a normal SDI-12 sensor and does not make sensor “measurements”. Instead,
the Measure command copies the most recently captured SDI-12 data parameter. If the module
mode is “Monitor”, the aM! can be used to read the most recent data the H-4161 has captured. If
the module mode is “Initiate”, the aM! command reads the most recent measurement made on the
auxSDI port.
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" may be 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 any time after the service request is received or the specified processing time
has elapsed.
The aM! command takes 0 seconds to complete and places 1 value in the sensor buffer, no service
request is sent.
Example of a H-4161 "aM!" command:
Command Response Time Values Description
"aM!" "a0001" 0 sec 1 Make measurement
Subsequent Command Response
"aD0"
a+AA.AAA
where: AA.AAA
= Most recent measurement (feet, inches, meters etc.)