Emerson Autochangeover Controllers AC8 - Manual (Page 51)

System and Control Options
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7.5.7 Define Sensor as Alarmable or Event
Each sensor may be defined as Alarmable (AL) or as an Event (EV).
• For a sensor defined as alarmable, the following alarm reactions
occur when the high-setpoint threshold is crossed: the LCD flashes,
the audible horn sounds, configured pager numbers will be notified
and a record is entered in the Alarm Log.
• For a sensor defined as an event, the high-setpoint occurrence is
recorded in the Event Log.
By default, all sensors are set up as AL (Alarmable).
• From the Setup Sensor Menu, choose Alarm/Event, as shown at
right, and press Enter ↵ .
• To change the type of sensor, use the arrows ↑↓ to choose
AL (Alarmable) or EV (Event), then press Enter ↵ .
7.5.8 Set Up Alarmable Sensors in Latched or Unlatched Mode
Alarmable sensor points may be set up in Latched mode (Y), requiring
the user to clear the AC8 alarms after an alarm has occurred, or
Unlatched mode (N), meaning that alarms will automatically clear
after a return-to-normal state. The default setting for alarmable sen-
sors is N (Unlatched). Any sensor defined as an event is automatically
Unlatched.
A sensor defined as Latched does not reset automatically after an
alarm. It will remain in the triggered position even after the monitored
sensor returns to normal. After an alarm, the user must manually
reset Latched sensors, as described in 7.13.1 - Clear Active Alarms.
This also means that any digital outputs linked to a Latched sensor
will remain triggered until the sensor is manually reset.
A sensor defined as Unlatched will automatically track the status of
the monitored sensor. No action by the user is required.
• From the Setup Sensor Menu, choose Latched, as shown at right,
and press Enter ↵ .
• To change this feature, use the arrows ↑↓ to choose Y (Yes -
Latched) or N (No - Unlatched), then press Enter ↵ .
NOTE: Only alarmable sensors may be set up as Latched. If you
attempt to set up an event as Latched, the message shown at right
appears. Press the ESC key to return to the previous screen to con-
tinue configuring the digital input.
The only way to reset latched alarms is by clearing active alarms. This
step is required to return latched points to their normal state. For
details, see 7.13.1 - Clear Active Alarms.
Setup Sensor Menu
SETUP SENSOR_1
CONNECTED: Y
LABEL: ROOM_TMP
↑↓
=NEXT
↵
=SELECT
UNITS: DEG
4 mA: +050.0
20 mA: +090.0
OFFSET: +005.0
> ALARM/EVENT: AL
LATCHED: N
LOW SETPT: +0050.0
HIGH SETPT: +0090.0
SENSOR DELAY: 00:01
Alarmable / Event
IS SENSOR AN ALARM
OR EVENT? AL
↑↓
=AL/EV
↵
=END
Setup Sensor Menu
SETUP SENSOR_1
CONNECTED: Y
LABEL: ROOM_TMP
↑↓
=NEXT
↵
=SELECT
UNITS: DEG
4 mA: +050.0
20 mA: +090.0
OFFSET: +005.0
ALARM/EVENT: AL
> LATCHED: N
LOW SETPT: +0050.0
HIGH SETPT: +0090.0
SENSOR DELAY: 00:01
Latched / Unlatched
IS ALARM
LATCHED? N
↑↓
=Y/N
↵
=END
Message (if sensor has
been defined as an event)
LATCH NOT ALLOWED
WHEN IN EVENT MODE
ESC=BACK