Port Latching; Boot Up; Mode Display And Control - Endress+Hauser Tankvision Multi Scan NXA83 Operating Instructions Manual

Tankvision
Endress+Hauser
If one of the field ports on the live system does not receive a correctly formatted reply for
longer than the timeout period (default 60 seconds), it will be marked as failed and initiate
a switch. This will cause the Multi Scan NXA83 to stop polling all field ports and switch to
Redundant Link mode. The second Multi Scan NXA83 will detect this change, switch to Live
Polling mode and start to poll all the field ports for gauge data.
During the switchover, no data will be lost and no gauging alarms will be raised in the Multi
Scan NXA83 or in any connected tank gauging software. An event will, however, be raised
on the Multi Scan NXA83 recording the switchover.
If, following the switch, the field port on the second Multi Scan NXA83 also fails to receive
correctly formatted data No Reply alarms will be generated.
If at any time an individual gauge fails on a port (i.e. does not reply), but other gauges are
returning valid data, the failed gauge will immediately be set to error and an alarm raised.
This will not trigger a switch.
4.2

Port Latching

If a port has failed on both Multi Scan NXA83 the system will "Latch" for that port. A Latched
port will not trigger redundancy mode switching. This state will remain until valid
communications is restored to the port. If the second Multi Scan NXA83 is not connected or
powered up, all ports will latch and no switching will occur.
Latching does not affect other ports, so if an Unlatched port fails redundant mode switching
will occur as normal.
4.3

Boot Up

Multi Scan NXA83 which are configured as "Switch by System" will initially boot up in
Redundant Link mode and check to see if there is a Multi Scan NXA83 in Live Polling Mode.
If a Multi Scan NXA83 in Redundant Link mode does not find a "Live" system within a timeout
period it will switch to Live Polling mode. The timeout period contains a random element, so
that if two Multi Scan NXA83 boot at exactly the same time, one should always switch to
Live Polling before the other.
If there are no Control Link connections between the two systems both will eventually switch
to Live Polling mode.
4.4

Mode display and control

The current redundancy mode may be displayed in the NXA83 runtime displays on the local
touchscreen.
A default screen is available on the configurator, although this may altered as required
during the configuration process.
Switch By System
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