Xylem H-4280 - Manual (Page 18)

3-6 SDI-12 Command and Response Protocol H-4280
3.5 Continuous Measurements
This is a new command for the Version 1.2 SDI-12 Specification. Sensors that are able to continuously
monitor the phenomena to be measured, such as a cable position, do not require a start measurement
command. They can be read directly with the R commands (R0!...R9!). The R commands work exactly like
the D (D0!...D9!) commands. The only difference is that the R commands do not need to be preceded with
an M command.
The H-4280 does not support the aR0! continuous measurement commands because the measurement and
math operations require several seconds to complete..
3.5 Send Acknowledge Command
The Send Acknowledge Command returns a simple status response which includes the address of the sensor.
Any measurement data in the sensor's buffer is not disturbed.
Command Response
"a!" "a<cr><lf>"
Where: a Is the sensor address ("0-9", "A-Z", "a-z", "*", "?").