BACnet Trend Log objects closely resemble standard NiagaraAX histories in many ways. However, a fully-compliant BACnet Trend Log includes additional data such as sequence numbers, as well as record entries for log events such as log enable, log disable, and buffer purge within the log data.
Therefore, depending on requirements, there are two methods to export a NiagaraAX history:
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Whenever a fully BACnet-compliant Trend Log object is needed, you must paste a special BacnetTrendLogExt extension (from the
bacnetpalette) into the source point in the station, instead of the typical history extension. In this case, the resulting history will provide the additional BACnet-compliant data such as sequence numbers and log events. For more details, see the next section BacnetTrendLogExt. -
If retroactively exporting to BACnet, and a Trend Log object that provides “by time” and “by index” access only is sufficient, export by simply selecting any “standard” Niagara history (created by a standard history extension). Do this in the Bacnet Niagara Log Export Manager, using a “Discover.” 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.
See Differences in BACnet-exposed histories for an example of how the histories differ.
Find BacnetTrendLogExts in the bacnet palette, under the Trending folder (Figure 93).
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 BacnetTrendLogExt extension types 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 parameters in the BacnetTrendLogExt history extension (of the source component), however, there are additional properties in its associated Bacnet Trend Log descriptor.
As found in the bacnet palette under the Trending, BacnetLogExtensions folder (Figure 93), the different types of BacnetTrendLogExt include:
In addition, there is a BacnetTrendLogAlarmSourceExt that you can paste under any of the extensions above. This provides intrinsic BACnet alarming/notification for buffer near-full events.
A Niagara history created by a BacnetTrendLogExt has extra fields for sequence numbers, and also “Log Events,” as shown in Figure 94.
Compare that with a “standard” Niagara history, as shown in Figure 95.
