Applies To:
  • CitectSCADA x.x

I have defined some Analog Alarms with the Rate field set to 10. What happens is that each time the value changes by an amount far less than the rate, momentary alarms are generated which clear almost immediately. How does the rate of change alarm work? 

A configuration with the Rate = 10 and the Alarm period = 60 seconds;

The alarm is tested each update of the [Alarm]ScanTime NOT each [Alarm]Period.

Therefore the Rate = 10/60. Any change greater than this slope will trigger the 'rate of change alarm' between scan time intervals. This is true if the value of the tag is rising or falling.

The alarm scan time parameter will tell Citect at what rate to process the alarms. This parameter defaults to 500ms. At this rate Citect will try to process the alarms every 500ms.