Additional information
● Additional information on the data structure of the OPC HDA is available in the specification
OPC Historical Data Access Specification V1.2
of the OPC Foundation.
6.4.4 Overview of supported attributes
Supported attributes
The following table lists the attributes supported by the OPC HDA server. Additional information
is available in the "OPC Historical Data Access Specification 1.20" of the OPC Foundation.
Attribute Attribute ID Description
ItemID OPCHDA_ITEMID Specifies which PCS 7 OS archive tag is accessed.
Item data type OPCHDA_DATA_TYPE Specifies the data type of the PCS 7 OS archive
tag.
Description OPCHDA_DESCRIPTION Outputs the description of the PCS 7 OS archive
tag. The description is specified in PCS 7 OS
TagLogging.
Engineering
Units
OPCHDA_ENG_UNITS Specifies the labeling of the unit shown in the
display. The labeling is specified in PCS 7 OS
TagLogging.
6.4.5 Overview of supported aggregate functions
Supported aggregate functions
The following table lists the aggregate functions supported by the OPC HDA server. Additional
information is available in the "OPC Historical Data Access Specification 1.20" of the OPC
Foundation.
Aggregate function Description
OPCHDA_COUNT Obtains the number of raw data for the specified period.
OPCHDA_START Obtains the start value of the raw data at the start time.
OPCHDA_END Obtains the end value of the raw data at the end time.
OPCHDA_AVERAGE Obtains the average value of the raw data for the specified
period.
OPCHDA_TIMEAVERAGE Obtains the time-weighted average value of the raw data for
the specified period.
OPCHDA_TOTAL Obtains the total value for the specified period.
OPCHDA_STDEV Obtains the standard deviation of the raw data for the
specified period.
OPCHDA_MINIMUMACTUALTIME Obtains the highest value and the time stamp of the raw data
for the specified period.
OpenPCS 7 interface
6.4 OPC Historical Data Access (OPC HDA)
OpenPCS 7
50 Function Manual, 05/2012, A5E02780178-02
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