7.22 BACnetTrendLogType
7.22.1 General
This OPC UA ObjectType represents an object that monitors a single property of a referenced object and logs its value and timestamp into an internal buffer when a set of pre-defined conditions are met.
Figure 31 shows an overview for the BACnetTrendLogType with its Properties and related ObjectTypes. It is formally defined in Table 39.
7.22.2 ObjectType definition
The BACnetTrendLogType ObjectType is formally defined in Table 39.
| Attribute | Value | |||||
| BrowseName | BACnetTrendLogType | |||||
| IsAbstract | False | |||||
| References | NodeClass | BrowseName | DataType | TypeDefinition | Other | |
|---|---|---|---|---|---|---|
| Subtype of the BACnetTrendLogBaseType defined in 7.20.3.10. | ||||||
| 0:HasProperty | Variable | COV_Resubscription_Interval | 0:UInteger | 0:PropertyType | O | |
| 0:HasProperty | Variable | Client_COV_Increment | BACnetClientCOV | 0:PropertyType | O | |
| 0:HasProperty | Variable | Log_DeviceObjectProperty | BACnetDeviceObject PropertyReference | 0:PropertyType | O | |
| 0:HasComponent | Variable | Log_Buffer | BaseDataType | 0:BaseData VariableType | M | |
The BACnetTrendLogType ObjectType is a concrete type and can be used directly.
7.22.3 ObjectType Description
7.22.3.1 Variable COV_Resubscription_Interval
This OPC UA Property, of DataType UInteger, represents the BACnet property COV_Resubscription_Interval.
The COV_Resubscription_Interval specifies the time in seconds between COV resubscriptions. The first COV subscription is issued when the trend log begins operations or when the Enable variable value becomes true.
7.22.3.2 Variable Client_COV_Increment
This OPC UA Property, of DataType BACnetClientCOV, represents the BACnet property Client_COV_Increment. The BACnetClientCOV DataType is defined in 10.6.3.
The Client_COV_Increment value indicates the increment that is used to determine whether a change of value has occurred.
7.22.3.3 Variable Log_DeviceObjectProperty
This OPC UA Property, of DataType BACnetDeviceObjectPropertyReference [], represents the BACnet property Log_DeviceObjectProperty. The BACnetDeviceObjectPropertyReference DataType is defined in 10.5.9.
The Log_DeviceObjectProperty variable specifies the Device Identifier, Object Identifier, and Property Identifier of the property to be trend logged.
7.22.3.4 Variable Log_Buffer
This OPC UA Variable represents the BACnet property Log_Buffer. It represents a list of logged values and can only be accessed with with the BACnet service ReadRange. Therefore, the OPC UA representation requires the AccessLevel HistoryReadable to allow access of the logged values through OPC UA Service HistoryRead (see Table 40).
The current value is not readable since it is not provided through BACnet directly. The BACnetUaMapper may provide the current value by reading the referenced BACnet property that is logged by the BACnet Trend Log object. In this case the AccessLevel can also have the Readable flag set.
| OPC UA Attribute | Value |
| BrowseName | Log_Buffer |
| AccessLevel | HistoryReadable |
| Historizing | True if BACnet property Enable is True and the current time is between the BACnet property values Start_Time and Stop_Time |