This OPC UA ObjectType represents the intrinsic configuration paremeters of a trend log. This primarily represents the basis upon which logging is performed: periodic, “triggered”, or based upon a change of value.

Figure 30 shows an overview for the BACnetTrendLogBaseType with its Properties and related ObjectTypes. It is formally defined in Table 38.

Figure 30 – BACnetTrendLogBaseType overview

The BACnetTrendLogBaseType ObjectType is formally defined in Table 38.

Table 38 – BACnetTrendLogBaseType Definition

Attribute		Value
BrowseName		BACnetTrendLogBaseType
IsAbstract		True
References	NodeClass		BrowseName	DataType	TypeDefinition	Other
Subtype of the BACnetLogType defined in 7.20.
0:HasProperty	Variable		Logging_Type	BACnetLoggingType	0:PropertyType	O
0:HasProperty	Variable		Log_Interval	0:UInteger	0:PropertyType	O
0:HasProperty	Variable		Align_Intervals	0:Boolean	0:PropertyType	O
0:HasProperty	Variable		Interval_Offset	0:UInteger	0:PropertyType	O
0:HasProperty	Variable		Trigger	0:Boolean	0:PropertyType	O

The BACnetTrendLogBaseType ObjectType is an abstract type and cannot be used directly.

This OPC UA Property, of DataType BACnetLoggingType, represents the BACnet property Logging_Type. The BACnetLoggingType DataType is defined in 10.4.16.

The Logging_Type value specifies whether the trend log collects record periodically, by change of value, or via “triggered” acquisition.

This OPC UA Property, of DataType UInteger, represents the BACnet property Log_Interval.

The Log_Interval value specifies a periodic value, in hundredths of a second, that the referenced property is logged when the Logging_Type variable value is POLLED. The variable value shall be zero and ignored when the Logging_Type variable value is anything other than POLLED.

This OPC UA Property, of DataType Boolean, represents the BACnet property Align_Intervals.

The Align_Intervals indicates whether clock-aligned periodic logging shall be enabled. When clock-aligned periodic logging is enabled, and the Log_Interval is a factor of a second, minute, hour, or day, then the beginning of the priod shall coincide with the next clock second, minute, hour, or day.

This OPC UA Property, of DataType UInteger, represents the BACnet property Interval_Offset.

The Interval_Offset value indicates an offset in hundredths of seconds from the beginning of the specified logging period until logging shall actually begin. The offset shall be interpreted as the Interval_Offset modulo the Log_Interval. For example, if the Log_Interval is 30 and the Interval_Offset is 31, then the offset shall be 1.

This OPC UA Property, of DataType Boolean, represents the BACnet property Trigger.

When the Trigger variable value transitions from true to false and the Logging_Type is TRIGGERED then the trend log shall serialize the referenced property. The Trigger variable value is reset to false when data acquisition is completed.