Campbell COM110A, Руководство пользователя

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Using with Campbell Scientific Dataloggers
31
10. Preventing COM110A modem Connection
Problems
The COM110A differs from previous modems offered by Campbell Scientific in
that it continuously monitors its connection state to the network. The modem will
reset itself if it loses connection which will often re-establish its connection to the
network. Generally, this will provide a reliable connection long term. However,
there is a very small chance that the COM110A modem could crash as a result of
electrical spikes on the power supply or local electrical storms. If the COM110A
modem is powered continuously, such a crash will often prevent it answering an
incoming call again until it has been reset.
To help overcome these problems, the datalogger can be programmed to either
reset the COM110A modem by sending it commands (see Appendix E) or to shut
down the COM110A modem at regular intervals using a power switch as
described in Appendix B. This will save power, but also ensures that the
COM110A modem is reset into a known state and make it re-register itself on the
network. To be sure that the COM110A modem resets properly, it must be turned
off for at least 10 seconds. How often the COM110A modem is turned off will
depend on the normal calling schedule, considerations of power consumption and
of how long you could afford to lose communication with the COM110A modem
if it did go offline.
When turning the power off to the modem it is advisable to avoid cutting the
power when the modem is online. The program examples in Appendix B check if
the modem is online before turning off the power. You should also avoid
scheduling calls to the logger when it is due to power off. If possible the
AT+CFUN=0 command should also be sent to the modem before cutting the
power to let the modem cleanly deregister from the network and shutdown its
radio modem (also shown in the example in Appendix B). If the modem is not
cleanly shutdown there may be a delay of some minutes before the network will
allow access to the modem again (and in GPRS mode, prevent modem from
establishing a PPP connection).
COM110A based CS-GSM/GPRS modems automatically monitor
their connection to the network and will reset the connection if the
modem believes it has not properly registered on the network for at
least 5 minutes.
11. Fault Finding
11.1 General
Before placing the COM110A modem out in the field it is important to check that
it is properly registered on a GSM network. To do this, connect it to a power
supply and turn on any power switch, if used, by connecting the power control line
to 5V or 12V. After power has been applied, the small LED in the case should
come on continuously initially. Within 30 seconds the LED should switch to start
to flash briefly every 2 seconds or so indicating that the unit has registered itself
successfully with a GSM network. As a second check, if the SIM contract allows
dialled calls to be made (this is not always allowed on GPRS only contracts)
connect it to a PC and, using a terminal emulation program, instruct it to dial a
valid telephone number, e.g.
ATD01509601091 <
ENTER
>. If the COM110A
modem does not cause the remote phone to ring but instead immediately responds
with a result of NO CARRIER it is likely that:
NOTE