Overview
IEC 62541-8:2015, titled OPC Unified Architecture - Part 8: Data Access, is an international standard developed by the International Electrotechnical Commission (IEC). This document is a key part of the OPC Unified Architecture (OPC UA) series, focusing specifically on the Data Access (DA) information model. The standard details additional VariableTypes, NodeClasses, Attributes, and Properties necessary for efficient and reliable Data Access operations within industrial automation and related sectors.
The second edition, published in 2015, updates and replaces the original 2011 edition to incorporate technical revisions including enhancements for handling ArrayItems, complex number DataTypes, and clarity around the deadband parameter. These improvements reflect the evolving requirements of device interoperability and data exchange consistency in automated and complex analyzer systems.
Key Topics
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Data Access Information Model
Defines the semantic structure required to represent automation data effectively. This includes specific VariableTypes such as DataItemType, AnalogItemType, DiscreteItemType, and new ArrayItemTypes for more complex data representations.
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VariableTypes and Complex DataTypes
The standard introduces support for complex number types and arrays used in devices like complex analyzers. This extension enables OPC UA to handle multidimensional and sophisticated data needed in diverse applications.
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Deadband Parameter Clarification
Deadband filtering is specified to be between 0.0 and 100.0, ensuring data quality and reducing unnecessary network traffic. Violations trigger the error code Bad_DeadbandFilterInvalid, enhancing robustness in data communication.
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Address Space Model
Detailed structuring of DataItems within the OPC UA Address Space facilitates better organization and navigation of processes and devices in an automation system.
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Attributes and Properties
The document systematically outlines attributes like Range, EUInformation (engineering unit details), and AxisInformation, critical for interpreting data values accurately.
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Data Access Status Codes
Provides comprehensive status and result codes categorizing data quality and operation results under various conditions, enabling precise diagnostics and error handling.
Applications
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Industrial Automation Systems
Facilitates standardized access to real-time and historical process data, enabling integration with supervisory control and data acquisition (SCADA) systems and programmable logic controllers (PLCs).
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Complex Analyzer Devices
The addition of complex number and array data types meets the needs of advanced instrumentation that measures multi-dimensional or complex data sets.
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Enterprise Integration
Supports seamless device-to-enterprise communication by defining a consistent and scalable Data Access model that bridges field devices with software at higher organizational levels.
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Process Control and Monitoring
Ensures robust, consistent data delivery with advanced filtering (deadband) and data quality monitoring, essential for critical control and monitoring applications.
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Manufacturing Execution Systems (MES) and Industrial Internet of Things (IIoT)
Provides the foundation for interoperable data exchange crucial for Industry 4.0 applications, enhancing system interoperability and data analytics.
Related Standards
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IEC 62541-1 to IEC 62541-7
Other parts of the OPC UA series covering general concepts, security, session management, and information modeling that complement Part 8’s Data Access functionalities.
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IEC 62541-9 (Alarms and Conditions)
Builds upon the Data Access model to handle notifications and event conditions effectively.
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ISO/IEC Directives, Part 2
Normative guidelines referenced for the publication and maintenance of this standard.
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UNECE Recommendations on Units of Measure
Referenced for EUInformation coding to ensure international consistency in engineering units representation.
Keywords: IEC 62541-8, OPC Unified Architecture, Data Access, DataItemType, AnalogItemType, ArrayItemType, deadband filtering, complex data types, industrial automation standards, OPC UA data model, process control interoperability, industrial data communication, IEC standards.
