CHAPTER 3 BASIC OPERATION
E5CK
3--8
•
The hysteresis of alarm outputs when alarms are switched ON/OFF can
be set as follows.
ON
OFF
Alarm hysteresis
Alarm value
Alarm value
ON
OFF
Upper limit alarm
Lower limit alarm
Alarm hysteresis
•
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 out-
put 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,” gener-
ally the process value is within the alarm range, and alarm output
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.
J
Close in alarm/open in alarm
•
When the controller is set to
“
close in alarm,” the status of the alarm out-
put function is output as it is. When set to
“
open in alarm,” the status of
the alarm output function is output inverted.
Alarm
Output
Output LED
Close in alarm
ON
ON
Lit
Close in alarm
OFF
OFF
Not lit
Open in alarm
ON
OFF
Lit
Open in alarm
OFF
ON
Not lit
•
Alarm type and close in alarm (normally open)/open in alarm (normally
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 [
] “close in 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
Alarm value
Alarm output
(close in alarm)
Standby sequence
canceled
PV
Alarm hysteresis
Time
Close (ON)
Open (OFF)
J
Alarm hysteresis
F
Standby
sequence
F
Summary of
alarm operations