Xylem SDI-12 RADAR - Manual (Page 27)

SDI-12 Command & Response
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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 any time after the service request is received or the specified processing time has elapsed.
example of an “am3!” command:
Command response Time Values Description
"am3!" “a0013” 1 sec 3 make measurement.
Subsequent Command response
"aD0" a+aa.aaa+BB.BBB+CC.C
where:
aa.aaa = Stage (feet, inches, meters etc.)
BB.BBB = Standard Deviation (feet, inches, meters etc.)
CC.C = Power Supply Voltage (Volts)
a concurrent measurement is one which occurs while other SDi-12 sensors on the bus are also
taking measurements. This command is similar to the “am!” command, however, the nn field has
an extra digit and the sensor does not issue a service request when it has completed the
measurement. Communicating with other sensors will NoT abort a concurrent measurement.
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
“aC!” “atttnn” initiate measurement
where:
a is the sensor address (“0-9”, “a-Z”, “a-z”, “*”, “?”).
C 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.
nn is a two digit integer (00-99) 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.
The data recorder may wake the sensor with a break and collect the data anytime after the specified
processing time has elapsed.
Concurrent measurement Command