Errors - Fault Conditions - Hanna Instruments HI 720 Instruction Manual

Many devices can be monitored through a remote modem, simply connecting
all the devices and the modem (or cellular module) to the same RS485 network.
Only one device can be configured through the item P .02 to answer to modem
calls, and this will control the modem or cellular module.
To avoid conflicts, never do any of the following actions:
• put more than one modem or cellular module in the same RS485 network
• set P .02 to "On" in more than one device in the same RS485 network
• set P .00 to "HI 504900 GSM module" in more than one device in the same
RS485 network (with HI 504900, SMSs can not be sent from more than one
HI 720)
• set P .02 to "On" in one device and P .00 to "HI 504900 GSM module" in
another one within the same RS485 network
• put a PC monitor within the RS485 network
Provided the above, any Hanna instrument with an RS485 port can be attached
to the network and monitored remotely.
When making a call, after the data connection is established, the "NNPWD..."
command (where "NN" is the address of the device controlling the modem, i.e.
the one with P .02 set to "On") must be issued by the remote computer within 15
seconds.
When the data connection is up, the RS485 protocol for a remote connection is
all the same as for a local network. An automatic disconnection takes place if no
character is received in the RS485 network in 3-4 minutes.
When a modem connection is up, the cellular module does not send any SMS.
If an error configured for SMS sending occurs, the relating alarm SMS will be
submitted by the HI 720 after modem disconnection.
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ERRORS - FAULT CONDITIONS

The below fault conditions may be detected by the software:
• EEPROM data error
• serial communication internal bus failure
• software dead loop
EEPROM data error can be detected through EEPROM test procedure at start-
up or when explicitly requested using setup menu, or during normal operational
mode if a checksum control fails.
When an EEPROM error is detected, a fault alarm
is generated according to the user configuration for
the EEPROM corruption error (see "Alarm - Error
configuration" section), and the user will be asked
to confirm or ignore a request of EEPROM reset.
If the request is ignored, the controller restarts operation, but alarm actions are
performed as configured by the user (see "Alarm - Error configuration" section).
Note that the device will be in Hold mode in any case.
If the reset action is confirmed, all the data stored in
the EEPROM are erased and the default values loaded.
After that, all calibrations must be performed
in order to obtain correct measurements.
The user will be informed that calibration is needed
through a "Do calibration!" message and a cali-
bration timeout error.
Any EEPROM reset is aborted without performing any
action if the user does not answer within 60 seconds.
When internal transmission is not acknowledged or a bus fault occurs for more than
a certain number of unsuccessful transmission attempts (due for example to a dam-
age occurred to one of the ICs connected to the internal bus), an internal bus error
is detected and the controller displays the message "Serial bus error".
If the error is due to impossible communication with the EEPROM or the RTC, all
the controller tasks are stopped, the alarm relay is de-energized, the red LED
blinks and the "Serial bus error" message will remain fixed on the display (repair
can not be postponed).
A software watchdog is provided in order to detect dead loop conditions or other
causes that make the software stuck. If it happens, a software reset is generated
after a time-out of 1 second.
At start-up the instrument checks if an RTC reset occurred since last software
initialization; if this is the case, the RTC is initialized with the default date and time
(01/01/2000 - 00:00). An EEPROM reset does not affect the RTC settings.
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