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.
Hysteresis
Different on/off switching thresholds.
Gap between switch-on and switch-off points (start pump at 20%, stop at 80%) that stops rapid cycling. Implemented in logic, thermostats, pressure switches, and alarm blocks.
Use the concept: 4–20 mA loop scaling · Industrial automation fundamentals · Modbus RTU CRC & frame helper
In depth
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.
OT backup and restore testing: prove the recovery path
Inventory the files and dependencies needed to recover a control system, set recovery objectives, and test restoration on an isolated target.