IEC 61131-3 PLC languages: which one to use
Ladder, function block, structured text, and the rest — what each of the five languages is good at and how shops actually mix them.
Function Block Diagram (FBD)
Signal-flow graphical PLC language.
IEC 61131-3 language where prebuilt blocks (timers, PID, math) are wired by signal lines. Natural for process and motion logic; pairs well with Structured Text for algorithms.
See also: IEC 61131-3 · Structured Text (ST) · PID loop
Use the concept: 4–20 mA loop scaling · Industrial automation fundamentals · Modbus RTU CRC & frame helper
In depth
PLC FAT and SAT checklist: test behavior and handover evidence
Plan factory and site acceptance around requirements, observable results, failure states, approved changes and recoverable project files.
PLC analog input scaling: raw counts, 4–20 mA and diagnostics
Map raw counts into engineering units, check the configured channel range, and keep signal-quality diagnostics separate from the displayed value.