Xylem SDI-12 RADAR - Manual (Page 22)

SDi-12 CommaND & reSPoNSe
20
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 "am!" command:
Command response Time Values Description
"am!" "a0044" 4 sec 4 make measurement
Note: The service request is normally sent within 530mS of receipt of the break.
Subsequent Command response
"aD0" a+aa.aaa+BB.BBB+CC+DD.D
where:
aa.aaa = Stage (feet, inches, meters etc.)
BB.BBB = Distance (feet)
CC = measurement Status:
0 = No errors
1 = 500ms response timeout
2 = response overflowed the buffer
3 = No preamble FF's
4 = missing start byte (delimiter)
5 = wrong delimiter
6 = wrong command byte
7 = response code not zero
8 = Field Device malfunction (Device Status = $80)
9 = wrong byte count byte
10 = Not enough bytes received
11 = Frame parity error
DD.D = Power Supply Voltage (Volts)
each SDi-12 data point or “measurement” is input from the radar subsystem. The “am!” command
does not filter or average the measurement data. The radar unit internally processes raw distance
measurements with a damping factor and other filtering algorithms.