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5.8 Alarm model ToC Previous Next

5.8.22 Rate of change Alarms ToC Previous Next

5.8.22.1 Overview ToC

A Rate of Change Alarm 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 Rate of Change Alarm becomes active when the rate at which the value changes exceeds or drops below a defined limit.

A Rate of Change 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.

5.8.22.2 NonExclusiveRateOfChangeAlarmType ToC Model

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 101.

Table 101 – NonExclusiveRateOfChangeAlarmType definition

Attribute Value
BrowseName NonExclusiveRateOfChangeAlarmType
IsAbstract False

Subtype of the NonExclusiveLimitAlarmType defined in clause 5.8.19.

References NodeClass BrowseName DataType TypeDefinition ModellingRule
HasProperty Variable EngineeringUnits EUInformation PropertyType Optional
           
ConformanceUnits          
A & C Non-Exclusive RateOfChange          

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.

5.8.22.3 ExclusiveRateOfChangeAlarmType ToC Model

ExclusiveRateOfChangeAlarmType is utilized with multiple mutually exclusive limits. It is formally defined in Table 102.

Table 102 – ExclusiveRateOfChangeAlarmType definition

Attribute Value
BrowseName ExclusiveRateOfChangeAlarmType
IsAbstract False

Inherits the Properties of the ExclusiveLimitAlarmType defined in clause 5.8.18.3.

References NodeClass BrowseName DataType TypeDefinition ModellingRule
HasProperty Variable EngineeringUnits EUInformation PropertyType Optional
           
ConformanceUnits          
A & C Exclusive RateOfChange          

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.

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