Appendix D. SDI-12 Sensor Support
D-2
D.1.3 Start Measurement Commands (aM!)
A measurement is initiated with
M!
commands. The response to each
command has the form atttnn, where
a
= sensor address
ttt
= time, in seconds, until measurement data are available
nn
= the number of values to be returned when one or more subsequent
D!
commands are issued.
D.1.4 Aborting a Measurement Command
A measurement command (
M!
) is aborted when any other valid command is
sent to the sensor.
D.1.5 Send Data Command (aDv!)
This command requests data from the sensor. It is normally issued
automatically by the datalogger after measurement commands
aMv!
. In
transparent mode, the user asserts this command to obtain data.
D.2 SDI-12 Transparent Mode
System operators can manually interrogate and enter settings in probes using
transparent mode. Transparent mode is useful in troubleshooting SDI-12
systems because it allows direct communication with probes. Datalogger
security may need to be unlocked before transparent mode can be activated.
Transparent mode is entered while the PC is in telecommunications with the
datalogger through a terminal emulator program. It is easily accessed through
Campbell Scientific datalogger support software, but is also accessible with
terminal emulator programs such as Windows HyperTerminal. Datalogger
keyboards and displays cannot be used.
The terminal emulator is accessed by navigating to the
Datalogger
menu in
PC200W
, the Tools menu in
PC400
, or the
Datalogger
menu in the
Connect
screen of
LoggerNet
.
The following examples show how to use
LoggerNet
software to enter
transparent mode and change the SDI-12 address of an OBS501 sensor. The
same steps are used to enter transparent mode with
PC200W
and
PC400
software after accessing the terminal emulator as previously described.
D.2.1 CR200(X) Series Datalogger Example
1.
Connect a single OBS501 to the CR200(X) (see TABLE
2.
In the
LoggerNet Connect
screen navigate to the
Datalogger
menu and
select
Terminal Emulator
. The terminal emulator window will open. In
the
Select Device
menu, located in the lower left-hand side of the window,
select the CR200Series station.
3.
Click on the
Open Terminal
button.