ABB DATUM L160 User Manual page 24

...4 CONFIGURATION MODE
...4.3.2 Alarms – Figs. 4.3, 4.4, 4.5 and 4.6
Process
Variable
Alarm On
Alarm Off
Information
Process Alarms –
above the high process alarm trip point value or falls below the low
process alarm trip point value. Process alarm trip point values are
configured in engineering units in Set Up Level (Level 2). If an alarm
hysteresis value of zero is configured the alarm becomes inactive when
the process variable value returns past the alarm trip point value. If a
positive or negative hysteresis value is configured the alarm becomes
inactive when the process variable reaches the hysteresis point. The
hysteresis value is configured in engineering units e.g. if a hysteresis point
five inches H
–5.0 is configured. The programmable alarm hysteresis function can also
be utilized for pump control applications when an output relay is assigned
to an alarm.
22
Hysteresis
High Process
an alarm becomes active when the process variable rises
0 below the alarm trip point is required, a hysteresis value of
2
Fig. 4.4 Process Alarms
Hysteresis
Low Process
Trip
Point
Alarm
On
Alarm
Off