5.8.23 Rate of change Alarms

5.8.23.1 Overview

A RateOfChangeAlarm is commonly used to report an unusual change or lack of change in a measured value related to the speed at which the value has changed. The RateOfChangeAlarm becomes active when the rate at which the value changes exceeds or drops below a defined limit.

A RateOfChangeAlarm is measured in some time unit, such as seconds or minutes and some unit of measure such as percent or meter. For example, a tank may have a High limit for the rate of change of its level (measured in meters) which would be 4 meters per minute. If the tank level changes at a rate that is greater than 4 meters per minute then the High sub state is entered.

5.8.23.2 NonExclusiveRateOfChangeAlarmType

The NonExclusiveRateOfChangeAlarmType is a special level Alarm utilized with one or more non-exclusive states. If for example both the High and HighHigh states need to be maintained as active at the same time this AlarmConditionType should be used

The NonExclusiveRateOfChangeAlarmType is based on the NonExclusiveLimitAlarmType. It is formally defined in Table 103.

EngineeringUnits provides the engineering units associated with the limits values. If this is not provided the assumed Engineering Unit is the same as the EU associated with the parent variable per second e.g. if parent is meters, this unit is meters/second.

5.8.23.3 ExclusiveRateOfChangeAlarmType

ExclusiveRateOfChangeAlarmType is utilized with multiple mutually exclusive limits. It is formally defined in Table 104.

EngineeringUnits provides the engineering units associated with the limits values. If this is not provided the assumed Engineering Unit is the same as the EU associated with the parent variable per second e.g. if parent is meters, this unit is meters/second.