
8/89 Device handbook A
PLUS
with / without LED display
,
157
679-19, 04/2016
3.3 Monitoring and alarming
The logic module integrated in the A
PLUS
is a powerful feature to monitor critical situations without delay
on device side. By implementing this local intelligence a safe monitoring can be realized which is
independent of the readiness of the control system.
3.3.1 Alarming concept
How alarms are handled is decided during the configuration of the device. For that in the logic module you
can define if LED's are used for alarm state display and how resp. when a possibly activated action, such
as the switching of a relay, will be reset. These configuration parameters are highlighted in yellow in the
following chart.
LED ON
Alarm
acknowledged
?
Alarm state
still persists ?
slow flashing
Y
Y
Y
N
N
Acknowledg.
of LEDS
required ?
Stop
flashing
LED OFF
Alarm state
still persists ?
N
Y
N
Fast
flashing
ALARM
LED used
for alarm
display ?
No action
N
Action
configurated
?
Perform action
Alarm state
still persists ?
Y
N
Action
resettable
?
Reset
?
Action reset
Y
N
N
Y
N
Y
Y
►
Acknowledgment
: This procedure affects the state of the LED only
If an alarm state is visualized via LED, its occurence must be acknowledged via display (
see:
Acknowledgment of alarms via display
), no matter if it is still active (fast flashing) or has dropped-out
already (slow flashing). By acknowledging an alarm, only the flashing of the LED stops, but a reset of the
alarm action is performed only if the display is configured as a possible source for alarm reset.
Acknowledgment is not required if "
acknowledgement of alarm LEDs required
" in the
logic module configuration is not selected.
►
Alarm reset
: This procedure affects the states of the follow-up action and the LEDs
If an alarm state occurs a follow-up action (e.g. the switching of a relay) can be triggered. This follow-up
action is normally reset as soon as the alarm condition no longer exists. But the alarm handling may be
configured as well in a way that only by means of an alarm reset the subsequent operation is withdrawn.
This way an alarm remains stored until a reset is performed, even if the alarm situation no longer exists.
Possible sources for an alarm reset are the display, a digital input, another logical state of the logic
module or a command via the bus interface.
Hint
: If an alarm is reset, the alarm state visualized via LED is acknowledged at the same time.
On the next page some signal flow examples are shown.