Classification standards and basic types of PLC

PLC Types & Standards

2026 Industrial Intelligence Report

PLCs come in types and follow standards. Here's the breakdown—from field experience.

Three Types

1. Compact (Brick)

I/O: Fixed, 10-100

Use: Simple apps

Example: Micro PLCs

2. Modular

I/O: Expandable

Use: Medium systems

Example: CompactLogix

3. Rack-Mounted

I/O: Hundreds

Use: Large systems

Example: ControlLogix

Standards

Standard Focus Description>
IEC 61131-3 Programming 5 languages defined
NEMA ICS 2-230 Environment Enclosure types

IEC 61131-3 is the global standard—ladder, FBD, ST, IL, SFC. Every modern PLC supports it.

— Senior Controls Engineer

Programming Languages

Language Abbreviation Use>
Ladder Diagram LD 60%
Function Block FBD Process
Structured Text ST Complex
Sequential Function Chart SFC Sequencer
Pro-Tip: Choose type based on I/O needs—compact (<100 I/O), modular (100-500), rack (>500).

Buy room to grow—but don't over-spec.

FAQ

+Most common type?
Compact—most applications don't need over 100 I/O. Low cost, simple.
+IEC 61131-3 required?
Not by law—but expected. All major PLCs support it. Required by most specifications.
+Specialty types?
Safety PLCs (safety circuits), motion PLCs (high-speed). Use for specialized apps.

Need Help Selecting?

We help select right PLC type.

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