Hazardous area classification, explained
Zones, divisions, gas groups and temperature classes decide which equipment may sit in a classified area. IP and NEMA ratings answer a different question.
Cascade control
Nested loops: master sets slave SP.
Two loops in series: the primary (master) loop writes the setpoint of the faster secondary (slave) loop. Rejects inner disturbances early; common in temperature-with-flow and level-with-flow schemes.
See also: PID loop · Control loop
Use the concept: 4–20 mA loop scaling · Process instrumentation: signal, measurement and control · Compressed air leak cost calculator
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.