OPC UA

OPC UA is not tied to Microsoft Windows or any specific operating system. It runs on everything from embedded ARM microcontrollers and Linux-based edge gateways to cloud servers. This is achieved through a layered architecture that abstracts the core services from the underlying platform APIs.

• ANSI C/C++, .NET, and Java stacks are common.
• Enables direct integration from the sensor to the cloud without OS lock-in.

All data—current values, historical logs, and alarms—is represented as interconnected Nodes in a single, object-oriented graph. This eliminates the fragmented namespace problem of Classic OPC.

• A temperature sensor isn't just a value; it's a Node with attributes for engineering units, alarm limits, and a relationship to the equipment it monitors.
• Clients can browse and discover the entire structure dynamically.

Security is built into the transport layer, not bolted on. OPC UA uses X.509 Certificates for application authentication and establishes a Secure Channel with encryption and signing.

• Supports multiple Security Policies like AES-256 and SHA-256.
• Role-Based Access Control (RBAC) restricts access to specific Nodes and methods, allowing read-only access for operators and configuration rights for engineers.

OPC UA allows industries to define formal, object-oriented schemas called Information Models. These models turn raw data into semantically meaningful information that machines can understand.

• Companion Specifications extend the base model for specific verticals like robotics, machine vision, and machinery.
• Enables true plug-and-produce interoperability where a client can discover the capabilities of a new device without manual mapping.

OPC UA supports both a transactional Client-Server model and a decoupled PubSub model to cover all industrial use cases.

• Client-Server: Used for secure, session-based command and control where a client requests data or calls a method on a server.
• PubSub: Used for efficient, one-to-many data streaming from a publisher to multiple subscribers, often over MQTT for cloud integration or TSN for deterministic field-level control.

The OPC UA framework defines a comprehensive set of services beyond simple data reads. These services are grouped into functional profiles.

• Data Access: Read, write, and monitor real-time values with a Deadband Filter to suppress noise.
• Alarms & Conditions: A stateful eventing model for tracking, acknowledging, and confirming abnormal situations.
• Historical Access: Retrieve and aggregate time-series data from an embedded historian for trend analysis.
• Method Calling: Remotely execute commands on a server, like triggering a calibration routine.