Instruction Manual

949-1190-1 Page 12 December, 1998
ABSOLUTE ALARMS
DEVIATION ALARMS
ALARM TYPE AND ACTION (if present)
Caution: In any critical application where failure could
cause expensive product loss or endanger personal safety,
a redundant limit controller is required.
When setting an alarm value for an absolute alarm (ALt = AbS), simply
set the value at which the alarm is to occur.
When setting the alarm value for a deviation alarm (ALt = dE), set the
difference in value from the Set Point (SP) desired. For example if a low
alarm is required to be 5 degrees below the SP, then set ALLo to -5. If
a high alarm is required 20 degrees above the SP, then set ALHi to +20.
If SP is changed, the alarm will continue to hold the same relationship
as originally set.
The diagram at the below shows the action and reset functions for both
absolute and deviation alarms.
When Alarm Power Interrupt, ALPi, is programmed ON and Alarm
Reset, ALrE, is programmed for Hold, the alarm will automatically reset
upon a power failure and subsequent restoration if no alarm condition is
present.
WARNING: IF INHIBIT IS ON AND A POWER FAILURE OCCURS DURING A HIGH
ALARM
, RESTORATION OF POWER WILL NOT CAUSE THE ALARM TO OCCUR
IF
THE PROCESS VALUE DOES NOT FIRST DROP BELOW THE HIGH ALARM
SETTING
. DO NOT USE THE ALARM INHIBIT FEATURE IF A HAZARD IS
CREATED
BY THIS ACTION. BE SURE TO TEST ALL COMBINATIONS OF HIGH AND LOW
ALARM
INHIBIT ACTIONS BEFORE PLACING CONTROL INTO OPERATION.