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CHAPTER 3 BASIC OPERATION
J Alarm hysteresis
F Standby
sequence
J Close in alarm/open in alarm
F Summary of
alarm operations
3--10
• The hysteresis of alarm outputs when alarms are switched ON/OFF
can be set as follows.
Upper limit alarm
Alarm hysteresis
ON
OFF
Alarm value
• Alarm hysteresis is set independently for each alarm in the "alarm 1
to 3 hysteresis" parameters (level 2 mode). Factory setting is "0.02:
0.02%FS".
• "Standby sequence" is a function for unconditionally turning alarm
output OFF when the process value has left the alarm range once and
it next enters the alarm range.
• For example, when the alarm type is set to "deviation lower limit,"
generally the process value is within the alarm range, and alarm out-
put become ON as it is as the process value when the power is turned
ON is smaller than the set point. However, if the alarm type is set to
"deviation lower limit with standby sequence", alarm output first
becomes ON when the process value exceeds the alarm setting value
to leave the alarm range and once again falls below the alarm value.
• When the controller is set to "close in alarm," the status of the alarm
output function is output as it is. When set to "open in alarm," the
status of the alarm output function is output inverted.
Close in alarm
Close in alarm
Open in alarm
Open in alarm
• Alarm type and close in alarm (normally open)/open in alarm (nor-
mally close) can be set independently for each alarm.
• Close in alarm/open in alarm is set in the "alarm 1 to 3 open in
alarm" parameters (setup mode). Factory setting is [
alarm".
The figure below visually summarizes the above description of alarm
operations (when alarm type is set to "lower limit alarm (deviation)
with standby sequence"):
Alarm type: lower limit alarm (deviation)
with standby sequence
PV
Alarm value
Standby sequence
canceled
Alarm output
(close in alarm)
Lower limit alarm
ON
OFF
Alarm value
Output
Alarm
ON
ON
OFF
OFF
ON
OFF
OFF
ON
Alarm hysteresis
Close (ON)
Open (OFF)
Alarm hysteresis
Output LED
Lit
Not lit
Lit
Not lit
] "close in
Time
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