Dwyer 2500 User Manual
Page 12
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.
W
ARNING
: I
F
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
. D
O
NOT
USE
THE
A
LARM
I
NHIBIT
FEATURE
IF
A
HAZARD
IS
CREATED
BY
THIS
ACTION
. B
E
SURE
TO
TEST
ALL
COMBINATIONS
OF
HIGH
AND
LOW
ALARM
INHIBIT
ACTIONS
BEFORE
PLACING
CONTROL
INTO
OPERATION
.