4. In response, the query
Select SDI12 Port:
is presented with a list of available ports.
Enter the port number assigned to the terminal to which the SDI-12 sensor is connected,
and press Enter.
5. In answer to
Enter timeout (secs):
type
100
and press Enter.
6. In response to the query
ASCII (Y)?
, type
Y
and press Enter.
7. SDI-12 communications are then opened for viewing.
9.8.2.1 SDI-12 transparent mode commands
SDI-12 commands and responses are defined by the SDI-12 Support Group (
) and
are available in the
. Sensor manufacturers determine which commands to
support. Commands have three components:
l
Sensor address ( a): A single character and the first character of the command. Sensors are
usually assigned a default address of zero by the manufacturer. The wildcard address ( ?) is
used in the
Address Query
command. Some manufacturers may allow it to be used in
other commands. SDI-12 sensors accept addresses 0 through 9, a through z, and A through
Z.
l
Command body (for example, M1): An upper case letter (the “command”) followed by
alphanumeric qualifiers.
l
Command termination ( !): An exclamation mark.
An active sensor responds to each command. Responses have several standard forms and
terminate with
<CR><LF>
(carriage return–line feed).
9.9 Ground loops
A ground loop is a condition in an electrical system that contains multiple conductive paths for
the flow of electrical current between two nodes. Multiple paths are usually associated with the
ground or 0 V-potential point of the circuit. Ground loops can result in signal noise,
communications errors, or a damaging flow of ground current on long cables. Most often,
ground loops do not have drastic negative effects and may be unavoidable. Special cases exist
where additional grounding helps shield noise from sensitive signals; however, in these cases,
multiple ground conductors are usually run tightly in parallel without conductive shielding
material placed between the parallel grounds. If possible, ground loops should be avoided.
When problems arise in a system, ground loops may be the source of the problems.
See also
9. Tips and troubleshooting
142