OPC DA (OPC Data Access) was the first OPC standard and, in 1996, laid the foundation for an entire family of vendor-neutral communication standards in automation and measurement technology. It was developed to transmit real-time data according to the Client-server model between devices, programmable logic controllers (PLCs), and human-machine interfaces (HMIs). Data is transmitted serially—that is, sequentially in individual data packets—with the OPC protocols handling the actual data transfer via TCP/IP can be set up and integrated into virtually any existing Ethernet network.
The problem that OPC DA solves
Before the introduction of OPC, exchanging data between devices from different manufacturers was a complex undertaking: Each product required its own driver-specific interface to communicate with other systems. For example, if you wanted to connect measuring devices, PLCs, and visualization software from different vendors, a custom driver was required for each individual combination—a significant burden in terms of system integration, maintenance, and expansion. OPC DA replaces this driver-specific data exchange with a universal standard. For each device or PLC, only a single, standardized OPC driver needs to be configured, through which any OPC-compatible software can then access the data. This eliminates the need to implement a separate interface for each manufacturer and each system.
Significance for Measurement Technology
In industrial measurement data acquisition and test bench automation in particular, components from a wide variety of manufacturers are often used together: sensors, measurement amplifiers, controllers, actuators, and higher-level control systems. OPC provides a common language that allows these systems to communicate with one another regardless of their respective manufacturers. For users in measurement technology, this means significantly simpler system integration: New devices can be connected via a standard OPC driver, rather than having to develop a custom solution for every new combination of devices.
From OPC DA to OPC UA
Although OPC DA was groundbreaking, it also had its limitations: The standard was based on Microsoft’s COM/DCOM technology and was therefore fundamentally tied to Windows systems; furthermore, it did not offer end-to-end security mechanisms for communication across enterprise and network boundaries. As a result, a further development was therefore OPC UA (OPC Unified Architecture) created. „UA“ stands for „Unified Architecture“ and refers to the current, platform-independent generation of the OPC standard. OPC UA —unlike OPC DA—is no longer dependent on a specific operating system, transmits data in an encrypted and authenticated manner, and also combines the functions of earlier OPC variants such as Data Access (real-time data), Historical Data Access (HA; historical, archived measurement data), and alarms into a single, unified standard. OPC UA thus meets the requirements of modern, end-to-end networked architectures, as needed in the context of Industry 4.0 and the Industrial Internet of Things (IIoT)—from the sensor and field level through PLCs and control systems all the way up to the cloud.
OPC at Delphin – Practical Applications
Delphin Technology consistently implements both standards in its product portfolio. The measurement technology software ProfiSignal has had an OPC client interface for many years, which allows third-party hardware from a wide variety of manufacturers to be integrated. In addition, both the central measurement data management software Delphin Data Center As well as the data loggers in the Expert, Loggito, and ProfiMessage series, they offer full OPC UA compatibility: as OPC UA clients, OPC UA servers, and OPC UA HA servers for the convenient transfer of historical measurement data. The high-performance measurement database developed by Delphin enables data transfer rates of up to 500,000 data points per second and supports up to 20,000 OPC UA nodes—allowing even large raw data streams, such as those from vibration measurements, can be reliably transmitted via OPC UA.