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.
• 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
Output
0
Time in seconds
Counter
Started
Example shows time hysteresis set to 70 seconds used with a high process alarm
10
Fig. 3.3 High and Low Process Alarm with Hysteresis
40 0
Counter Counter
Reset Started
Time Hysteresis Status
Fig. 3.4 Time Hysteresis Alarm
70 130
Hysteresis Time Counter
Elapsed Reset
Hysteresis
Trip Point
Hysteresis
Alarm On
Alarm Off
Alarm On
Alarm Off
Alarm Trip Point
Alarm On
Alarm Off