9. Operation
9.1 SDI-12 sensor measurements
The SDMS40 responds to the SDI-12 commands shown in
(p. 12). When using an
M!
command, the data logger waits for the time specified by the sensor, sends the
D!
command,
pauses its operation, and waits until either it receives the data from the sensor or the sensor
timeout expires. If the data logger receives no response, it will send the command a total of three
times, with three retries for each attempt, or until a response is received. Because of the delays
this command requires, it is only recommended in measurement scans of 10 seconds or more or
use
SlowSequence
.
A
C!
command follows the same pattern as an
M!
command with the exception that it does not
require the data logger to pause its operation until the values are ready. Rather, the data logger
picks up the data with the
D!
command on the next pass through the program. Another
measurement request is then sent so that data is ready on the next scan.
The
R0!
command directly reads the sensor measurements and outputs all of its values.
NOTE:
This section briefly describes using the SDI-12 commands. Additional SDI-12 information is
available in
(p. 31), or at
.
Table 9-1: SDI-12 command list
Commands
1
Responses
Remarks
a!
a<CR><LF>
Acknowledge active.
al!
“system info” <CR><LF>
SDI012 version, manufacturer, model, firmware
version (e.g. 013wtherpiaSDMS40v6.111-24-
2016).
aV!
“test result” <CR><LF>
System verification details.
aAB!
B<CR><LF>
Change address.
A?!
a<CR><LF>
Query sensor address.
aM!
0501<CR><LF>
Start measurement. Average depth value will
be provided by
aD0!
following a service
request.
SDMS40 Multipoint Scanning Snowfall Sensor
12
