History export
Therefore, depending on requirements, there are two methods to export a history:
- When a fully BACnet-compliant trend log object is needed, you must dragBacnetTrendLogExt extension from the bacnet palette into the source point in the station, instead of the typical history extension. In this case, the resulting history provides the additional BACnet-compliant data, such as sequence numbers and log events.
- If retroactively exporting to BACnet, and a trend log object that provides data by time and by index, access only is sufficient. Export by selecting any standard history (created by a standard history extension). Do this in the Bacnet Niagara Log Export Manager using a discover job. In this case, the exposed trend log object does not provide sequence numbers or by sequence number access, because this information was not stored within the original history.
BacnetTrendLogExt extensions
The BacnetTrendLogExts reside in the Trending folder of the bacnet palette.
Figure 11. BacnetTrendLogExts in the bacnet palette
You can use one of these instead of a standard history extension, pasting it in any point in which you need to export its history as a fully BACnet-compliant trend log object. For example, if you have a Lon proxy point of type NumericPoint, for nvoSpaceTemp representing room temperature, you could copy a BacnetNumericIntervalTrendLogExt into that NumericPoint. Its resulting history (created only after you enable it, as with any history extension) will now be fully BACnet-compliant.
By default, when you add one of the extensions to a component, note that a corresponding Bacnet log descriptor of type BacnetTrendLogDescriptor is automatically created in the root of the Export Table. You still define the normal collection properties in the BacnetTrendLogExt history extension (of the source component), however, there are additional properties in its associated BACnet trend log descriptor.
Differences between BACnet-exposed histories and standard histories
A history created by a BacnetTrandLogExt has extra properties for sequence numbers and log events. A standard history does not include these properties.