Safety instrumented systems: the boundary between control and protection
Basic SIS and SIF concepts, independence, SIL targets, proof testing, bypasses, and the questions to answer before connecting safety to a control system.
SIL
Quantified reliability target for safety functions.
Safety Integrity Level (1–4): the quantified reliability target for a safety function per IEC 61508/62061. Higher SIL means lower tolerable probability of dangerous failure — and stricter development and verification demands.
See also: Functional safety · PLC
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.