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Alarm Hysteresis Section 4-2
4-2 Alarm Hysteresis
• The hysteresis of alarm outputs when alarms are switched ON/OFF can
be set as follows:
• Alarm hysteresis is set independently for each alarm in the “alarm hyster-
esis 1”, “alarm hysteresis 2” and “alarm hysteresis 3” parameters
(advanced function setting level). Default is “0.2”.
4-2-1 Standby Sequence
• “Standby sequence” is a function which allows the alarm outputs to be
temporarily disabled while the first alarm condition occurs. From here on,
the alarm output is active for future alarm conditions.
• For example, with a lower limit alarm, the process value will normally be
below the set point, i.e., within the alarm range, when the power supply is
turned ON, causing an alarm to be output.
If the lower limit alarm with a standby sequence is selected, an alarm will
not be output until the process value increases above the alarm set value,
i.e., until it leaves the alarm range, and then falls back below the alarm set
value.
Restart • The standby sequence is canceled when an alarm is output. It is, how-
ever, restarted later by the “standby sequence reset” parameter
(advanced function setting level).
For details, see the “standby sequence reset” parameter in Section 5
Parameters.
4-2-2 Alarm Latch
• The alarm latch can be used to keep the alarm output ON regardless of
the temperature once the alarm output has turned ON. The alarm output
will turn OFF when the power is turned OFF.
• (The alarm output can also be turned OFF by switching to the initial set-
ting level, communications setting level, or advanced function setting
level.)
Alarm value
Upper-limit
alarm
Alarm hysteresis
Alarm value
Lower-limit
alarm
Alarm hysteresis
ON
OFF
ON
OFF
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