Contents and methods of determining the PLC model and its hardware configuration
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Contents and methods of determining the PLC model and its hardware configuration
Picking the right PLC in 2026 is no longer just about counting I/O. With OPC UA over TSN, IEC 62443 cybersecurity, and CIP Safety 2.0 now baked into most control platforms, a sound selection methodology must weigh networking, safety, security, and lifecycle , rather than just the size of the rack.
Detail
Eight selection criteria, not three: I/O count, scan time, memory, communication, safety, cybersecurity, environment, and lifecycle.
Add 20, 30% I/O headroom in 2026 , fieldbus convergence and edge I/O have changed the meaning of “point count.”
Reflash a 2024-vintage selection matrix with OPC UA over TSN, IEC 62443-4-2 SL2, and CIP Safety 2.0 before quoting.
Two years ago, the typical “how to choose a PLC” article boiled down to: count I/O, estimate scan time, check memory. That mental model dates from the 1990s, when a controller was a stand-alone box wired to discrete 24 V inputs. In 2026, that box is the edge of an industrial network, and four things have shifted under the engineer’s feet:
PROFINET over TSN, EtherNet/IP with CIP Sync, and OPC UA over TSN now share a single physical layer. The PLC is the convergence node, not an isolated controller.
CIP Safety 2.0, PROFIsafe over PROFINET, and Safety over EtherCAT let one CPU run standard and safety logic in parallel. The hard-wired safety relay is becoming a fallback.
IEC 62443-4-2 Security Level 2 (SL2) is the de-facto floor for OT procurement in water, pharma, and energy. A 2024 datasheet often does not list the SL level , a 2026 selection matrix must.
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