Xylem SDI-12 RADAR User Manual
Page 29
SDI-12 Command & Response
27
The data recorder may wake the sensor with a break and collect the data anytime after the specified
processing time has elapsed.
The Send Data command returns sensor data generated as the result of previous “am!”, “am1!”,
“aC!”, or “aV!” commands. Values returned will be sent in 33 characters or less. The sensor’s data
buffer will not be altered by this command.
Command
response
“aD0!” through “aD9!”
“apd.d ... pd.d
where:
a
is the sensor address (“0-9”, “a-Z”, “a-z”, “*”, “?”).
D0...D9
areupper-case aSCii character
p
is a polarity sign (+ or -)
d.d
represents numeric digits before and/or after the decimal. a decimal may be
used in any position in the value after the polarity sign. if a decimal is not used,
it will be assumed to be after the last digit.
For example: +3.29 +23.5 -25.45 +300
if one or more values were specified and a “aD0!” returns no data (
measurement was aborted and a new “m” command must be sent.
Send Data Command
example of an “aD0!” command:
Previous Command response
"am!"
“a0044
Note: The service request is normally sent within 530mS of receipt of the break.. The 4-second
value reported allows time for a few retries when communicating with the radar subsystem.
Subsequent Command
response
"aD0"
a+aa.aaa+BB.BBB+CC.C
where:
aa.aaa
= Stage (feet, inches, meters etc.)
BB.BBB
= Distance (feet)
CC
= measurement Status
DD.D
= Power Supply Voltage (Volts)