59
Command
Response
Comment
a
0M! 00013<CR><LF>
3 values are available in 1 second
b
0D0! 0+1.1+2.2+3.3><CR><LF>
3 values:
1.1
,
2.2
,
3.3
c
1M! 10022<CR><LF>
2 values are available in 2 seconds
d
1D0! 1+4.4+5.5<CR><LF>
2 values:
4.4
,
5.5
e
2M! 20031<CR><LF>
1 value is available in 3 seconds
f
2D0! 2+6.6<CR><LF>
1 value:
6.6
Figure 23: Principal of data acquisition by SDI-12
At the beginning of each measurement interval the MRL-7 sends an
M!
command to the first sensor
(a). The sensor answers by returning the number of available measurements and the measurement
duration. After the required measurement time the MRL-7 sends a
D!
command to request the meas-
urement results (b). This sequence is repeated for the other two sensors (c … f) before the next meas-
urement interval starts.
For a detailed description on SDI-12 communication please refer to
9.4.2
Measurement intervals
The measurement interval of all sensors is specified in
9.4.3
Measurements with an SDI-12 sensor
An SDI-12 sensor is wired to the MRL-7 as shown in
Figure 24: Wiring of a SDI-12 sensor