Your Loop Isn't Badly Tuned — The Valve Is Sticking: Finding Stiction in Trend Data
A level loop still cycling after two retunes is usually the valve. Reading stiction off PV/OP trends, proving it with a step test, and monitoring it.
Articles
Practical SCADA notes
Field-oriented references for HMI/SCADA systems, industrial communication, alarms, tags, historians, and project delivery.
Ratio Control: Blending Two Flows When You Only Get to Control One of Them
In ratio control one stream sets the pace and you trim the other. Where the multiplier goes, why actual ratio drifts, and starting up without off-spec.
Split-Range Control: Handing Off Between Two Valves Without a Bump at the Split Point
One PID driving a heating and a cooling valve stalls or hunts right at the changeover. Setting the split point, killing overlap, and the gain jump.
Cascade Control: Why the Slave Loop Has to Be Faster Than the Master
Cascade loops fail when the two are tuned in the wrong order or the slave's limits never reach the master. Commissioning them so they stop fighting.
Why Your PID Loop Overshoots Every Time the Valve Hits a Limit
Reset windup is why a well-tuned loop overshoots after saturation or a manual-to-auto swap. What anti-windup and external reset actually fix in a PLC.
Try a Live Operational State Tutorial
A short hands-on walkthrough that turns one temperature signal into alarm state, switch action, HMI feedback, and an event log using the StateX tutorial.