Xylem SDI-12 RADAR User Manual
Page 25
SDI-12 Command & Response
23
The radar only supports the”am2” measurement command when the Power mode = 1. 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.
when Power mode = 0, the radar returns “a0000” signifying the command is not supported in
this mode.
when Power mode = 1, the H-3611 averages the data collected from the previous minute and
returns the mean and standard deviation
.
The standard deviation is computed as follows:
1. Compute the mean for the data set
2. Compute the deviation by subtracting the mean from each value
3. Square each individual deviation
4. Divide by one less than the sample size
5. Take the square root
Command
response
Description
“am1!”
“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
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.
“am2” 1 minute average measure Command