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ChangeOfDiscreteValueAlarmExt (bacnet-BacnetChangeOfDiscreteValueAlgorithm)

This component is an AlarmSourceExt with the OffnormalAlgorithm property set to a BacnetChangeOfDiscreteValueAlgorithm.
This algorithm causes a toNormal event whenever the out-value changes for longer than the TimeDelayToNormal. You can apply it to any point type but it is designed for points that change by discrete values such as Boolean and Enum points.

It is available in the bacnet palette.

Figure 68.   BAlarmSourceExt with the offnormalAlgorithm property set to a BBacnetChangeOfDiscreteValueAlgorithm
Image

To set up alarming on a component you add an alarm extension to the component’s property sheet. Alarm extension types must match their parent component type.

Each alarm extension shares the same set of properties that specify the alarming conditions and certain routing options. Alarm extension properties define items such as alarm enable (annunciation) transition types, alarm delay times, associated alarm class, and alarm display text for different transition types. You define the actual alarm limits or state(s) in properties in the extension’s “Offnormal Algorithm slot.

Property Value Description
Alarm Inhibit true or false true prevents all alarm generation due to any transition or state change, thus preventing unintended alarms in after-hours situations when a piece of equipment is turned off.Inhibit Time qualifies this behavior.

For example, if set to true and an Offnormal state is reached, a toOffNormal status is not communicated. When the state returns to Normal, a toNormal status also is not communicated. This property also prevents alarm generation during the fault state.

A difference between Alarm Inhibit and Alarm Delay is that the former is a boolean value (true/false) and may be controlled by another device (for example, the ON/OFF value of a fan).

false allows alarm generation. This value prevents alarms from being inhibited (even if an Inhibit Time is set).

Inhibit Time hours minutes seconds Controls the length of time that the current Alarm Inhibit state remains in effect after an Alarm Inhibit state change.

When an Alarm Inhibit value changes from true to false, alarm generation continues to be inhibited for the time specified by the value set for Inhibit Time

When an Alarm Inhibit value changes from false to true, alarm generation may continue to be inhibited for a time that is dependent on the point type. For discrete points, the system increases the Inhibit Time value by a factor of three. If the point is a numeric point, nothing changes.

Alarm State NormalLow LimitHigh Limit orFault Displays the current state of the alarms.
Time Delay hours: minutes: seconds Displays the minimum time period that an alarm condition must exist before the object alarms. In other words, the object status must meet the alarm criteria for a continuous period equal to or greater than defined in the this property before an alarm is generated. Time Delay provides a way to prevent nuisance alarms that may be caused by a momentary change in a state value (Normal, Low Limit, High Limit).
 NOTE: Time Delay does not affect alarms generated by a fault. There is no delay when transitioning in or out of a Fault generated alarm.  
Time Delay to Normal hours: minutes: seconds Sets the minimum time period that a normal condition must exist before the object may return to normal status.
Alarm Enable toOffnormal ortoFault toOffnormal turns on the ability of the alarm to transition from normal to the alarm state Offnormal.

toFault turns on the ability of the alarm to transition from normal to the alarm state Fault.

To Offnormal Times text
When a point transitions to an offnormal state, reports four pieces of information:

Alarm Time displays when the alarm condition occurred.

Ack Time displays the time that the alarm was acknowledged.

Normal Time displays the time that the to-normal event occurred.

Count displays the total number of offnormal events.

To Fault Times text
When a point transitions to a fault state, reports four pieces of information:

Alarm Time displays the time that the to-fault event occurred.

Ack Time displays the time that the alarm was acknowledged.

Normal Time displays the time that the To Normal event occurred.

Count displays the total number of Offnormal events.

Time in Current State hours: minutes: seconds Displays the elapsed time since the component transition to the current state occurred.
Source Name %parent.displayName% (default) Displays the name of the alarm source. If you use the default script setting, the source name field shows the display name of the alarm extension parent. You can edit this script or type in a multi-line literal string to display.
To Normal Text text
Configures what displays when the component transitions to a normal status. When applicable, text entered for Fault Algorithm, High Limit Text and/or Low Limit Text may override this text.
To Fault Text text
Enters the text to display when the component transitions to a Fault status. When applicable, text entered for Fault Algorithm, High Limit Text and/or Low Limit Text may override this text.
To Offnormal Text text
Enters the text to display when the component transitions to an Offnormal (alarm) state. When applicable, text entered for Fault Algorithm, High Limit Text and/or Low Limit Text may override this text.
Hyperlink Ord or Hyperlink Ord, BQL Query or path
Associates an ORD, BLQ query or path with an alarm state on the component. When an alarm is reported in the console, the Hyperlink button activates. Clicking this button links to the location you specify here.
Sound File  
Configures the path to a sound file that plays when the current component is in an alarm state. Use the folder icon to browse to the file. Click the arrow icon to the right of the folder icon to test the path.
Alarm Icon ord Defines the path to a graphic file to add to the display in the timestamp column of the alarm table in the Console Recipient view.
Alarm Instructions text Opens a window in which you can provide customized instructions to the building attendant concerning how to handle the alarm.
Fault Algorithm additional properties Displays Fault options that depend on the alarm extension. You define the actual alarm limits or state(s) in subproperties in this slot.
Offnormal Algorithm additional properties
Displays offnormal options that depend on the alarm extension.
Ordinal read-only Provides a unique identifier for the particular OnCallList. The OnCallService tracks the next free ordinal number.
Alarm Class read-only used in Lists, console columns, or %alarmClass% on a report.
Defines alarm routing options and priorities. Typical alarm classes include High, Medium and Low. An alarm class of Low might send an email message, while an alarm class of High might trigger a text message to the department manager.
Meta Data text
Defines additional information for the extension.

Related Links

  • BacnetDevice (bacnet-BacnetDevice) (Parent Topic)

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