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Bacnet Trend Log Descriptor (bacnet-BacnetTrendLogDescriptor)

This component is the server descriptor that exposes a history created with a BACnet trend log extension as a BACnet trend log object. You can use the Bacnet Export Manager view of the BACnet Export Table to add, edit, delete, and access exported components.

Unlike a history exported with a Bacnet Niagara History Descriptor (created by a standard history extension), a history exported by a Bacnet Trend Log Descriptor appears as a fully BACnet-compliant trend log object. This means that it supports, by sequence number, requests in addition to by time requests from external BACnet devices. The driver creates these descriptors in the root of the BACnet Export Table when you copy one of the various trend log extensions into a component.

Only the following read-only properties qualify for initial value setting during object creation. Requests that include non-qualified properties from the client cause a request to fail.

  • Device Status Facets
  • Discovery History Type

  • Object Name
  • Description
  • Log Device Object Property
  • Notification Class
  • Notify Type
 NOTE: Niagara does not support setting the Log Device Object Property Reference value directly from Workbench. It is recommended that you set this property only through a Write Property BACnet call over the network. 
Figure 147.   Properties of BacnetTrendLogDescriptor
Image

You use the Bacnet Export Manager view of the Bacnet Export Table to add, edit, delete, and access exported components.

In addition to the common properties (Status and Fault Cause), this component has these properties.

Property Value Description
Event Detection Enable true (default) or false
Turns detection of an input event on (true) and off (false) for analog, binary and multi-state descriptors.
Bacnet Status Flag read-only indicator and check boxes
Configures four status flags for BACnet. These options are available to enable detection of specific status conditions.
Log Ord read-only Indicates the path of the selected trend log.
Object Id drop-down list and number (from 0 to 4194302)
Identifies each device and component by the type of entity (Object Id) combined with a unique Instance Number.

For devices (controllers, instruments, meters, etc.), Instance Number must be unique within the BACnet internetwork. For components (points, schedules, analog inputs, files, groups, multi state inputs, etc.), it must be unique within the device.

Object Name text in the format name.name.name.name (default includes the entire component path in the station using period (“/) delimiters between parent.child levels)
Identifies a BACnet object. This name should be unique within this specific device.

For components, this name includes the entire component path under the station’s Config using period (.) delimiters between parent.child levels. This enforces (externally) the BACnet requirement for unique names for all objects in a device.

For a proxy point, this is the default name in the station.

You can shorten or edit Object Name, however, each Object Name must be unique among all server descriptors under the Export Table.

Description text
Provides additional information, which could include the camera’s geographical location or other unique information.
 NOTE: After creation (adding) BACnet file descriptors, note that each descriptor also has additional properties accessible in its property sheet, along with those seen in the Add and Edit window.  
COV Resubscription Interval number
Specifies the length of time that the extension waits before initiating a re-subscription request.
Client COV Increment number to two decimal places
Specifies the minimum COV required before a COVNotification is issued to subscriber BACnet COV-clients.

Related Links

  • Server (Parent Topic)

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