ABB COMMANDER 1900 Series Programming Manual page 12

...3 BASIC CONFIGURATION LEVEL
3.4 Set Up Alarms
Information.
• Four alarms per channel – identified A1 to D1 (for channel 1) up to A4 to D4 (for channel 4).
• Three operator acknowledge options.
• Global alarm acknowledgment – by digital input, alarm, logic equation result or real time event (if option fitted).
• High/low process alarms.
• High/low output alarms.
• High/low deviation alarms.
• Fast/slow rate of change – of process variable alarms.
• Adjustable hysteresis value – to prevent oscillation of alarm state.
• Time hysteresis – to allow delayed triggering of alarms.
Process Variable
High
Process
Low
Process
Control
Output
High Output
Low Output
10
Fig. 3.3 High and Low Process with Hysteresis
Fig. 3.4 High and Low Output with Hysteresis
Hysteresis
Trip Point
Hysteresis
Alarm On
Alarm Off
Alarm On
Alarm Off
Hysteresis
Trip Point
Hysteresis
Alarm On
Alarm Off
Alarm On
Alarm Off