3-6 Process Alarms3-6 Process Alarms
The output 2 will perform process alarm function by selecting
ALM for OUT2 and PV.H.A or PV.L.A for AL.FN. If PV.H.A is
selected the alarm will perform process high alarm. If PV.L.A
is selected the alarm will perform process low alarm. The
process alarm sets an absolute trigger level. When the
process exceeds that absolute trigger level an alarm occurs.
The trigger level is determined by SP2 (Set point 2 value) and
AL.HY (Alarm hysteresis value). The hysteresis value is
introduced to avoid interference action of alarm in a noisy
environment. Normally AL.HY can be set with a minimum
value(0.1).
There are two types of alarm mode can be selected, these
are: normal alarm and latching alarm.
Normal Alarm: AL.MD= NORM
When a normal alarm is selected, the alarm output is de-
energized in the non-alarm condition and energized in an
alarm condition.
Normal Alarm: AL.MD= NORM
Latching Alarm: AL.MD= LTCH
If a latching alarm is selected, once the alarm output is
energized, it will remain unchanged even if the alarm
condition has been cleared unless the power is shut off or
the RESET key (or remote reset button) is pressed.
Latching Alarm: AL.MD= LTCH
Failure Transfer: AL.FT = OFF or ON
Sensor Break A-D FailureIn case of or occurs, the alarm
output will be on or off according to the selection of AL.FT.
Failure Transfer: AL.FT = OFF or ON
Sensor
Break A-D Failure
36
SP2 = 200
AL.MD = NORM
Examples:
AL.HY = 10.0
AL.FN = PV.H.A
Trigger levels for process high alarm are SP2 and SP2 AL.HY.
Trigger level for process low alarm are SP2+AL.HY and Sp2.
UM L91-Rev 8
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