Graphic & Text Symbols in PLC Circuit Diagrams — IEC 60617 / 81346 (2026)
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Graphic & Text Symbols in PLC Circuit Diagrams, IEC 60617 / 81346 (2026)
IEC 60617 and IEC 81346 remain the global reference for PLC schematic symbols and reference designations in 2026.
Detail
IEC 81346 has been harmonized into IEC 62491 since 2024, but the RD reference codes (-S, -K, -Q, -M) remain unchanged.
ANSI/NEMA symbols differ from IEC mainly on contactor coils and discrete relays; a 2024 annex closes the historical gap.
EPLAN, AutoCAD Electrical, and Studio 5000 libraries now ship ready-made IEC 60617/2024 symbol packs; outdated blocks are a top field-error source.
A 2026-ready PLC schematic uses IEC 60617 graphic symbols plus IEC 62491 reference designations, validated against vendor libraries before any wiring change.
If you wire panels, read P&IDs, or troubleshoot legacy PLC cabinets, two ISO/IEC standards still decide what shows up on your screen:
for the label. This Engineering Notes refresh walks through the 2026 picture, what changed since 2024, and where
Reference prefixes (-S sensor, -K relay, -Q breaker, -M motor) are unchanged in 2026.
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