OPC Introduction
An OPC server acts as a communication bridge between physical devices (such as PLCs) and client software (like SCADA, MES, or HMIs). It connects to industrial hardware using device-specific protocols (e.g., Modbus, Profibus) and then exposes this data using a standardized OPC interface. This abstraction allows client applications to access real-time machine data without needing to understand the native device protocol.
Troubleshooting Steps:
1. Verify Tag Updates
Check the last read time of relevant tags in the OPC server.
Ensure the tag values correlate with real-time machine data from the PLC or control system.
2. Validate PLC–OPC Connection
Confirm that the PLC is online and reachable from the OPC server machine.
Ensure correct IP address, port, rack/slot configuration, and that the PLC is in "Run" mode.
Restart the connection or rescan tags if needed.
3. Check Permissions and Security (especially for OPC UA)
Trust and install valid certificates on both the OPC server and the client.
Confirm that firewalls or antivirus software are not blocking required ports:
DCOM (OPC Classic): Often uses a wide range of dynamic ports.
Port 4840 (OPC UA): Ensure this port is open and not restricted.
Ensure appropriate read/write access is granted for the required OPC tags.
4. Review System Performance
Monitor the OPC server machine for high CPU or memory usage that could cause latency.
Check for network or I/O bottlenecks, especially when:
Polling a large number of tags.
Handling multiple OPC clients simultaneously.