IM/SM500F Rev. Z 103
Fig. 7.15 Delayed High/Low Process Alarms
Hysteresis
Alarm On
Alarm Disabled
Alarm Enabled
Trip Point
Alarm Off
Delay Time
Process
Variable
Process variable goes
above trip point but alarm
is not activated because
enable signal is low (Alarm
Disable).
Process variable goes
below trip (hysteresis)
point therefore alarm is
de-activated.
Alarm Enable signal is
switched On. Alarm delay
timer is started.
Process variable goes
above trip point but alarm
is not activated because
alarm delay time has not
expired.
Alarm delay timer expires,
alarm is now enabled. Alarm
is activated because process
variable is above trip point.
Process variable goes above
trip point, alarm is activated
(alarm is enabled and delay
time has expired).
Alarm Enable signal is
switched Off. Alarm is
disabled immediately.
Alarm de-activates.
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