Making Online PLC Edits Without Tripping the Running Process
Changing ladder logic in a running PLC safely: online edit versus download, scan-order traps, seal-in glitches, forces, and a pre-edit checklist.
Articles
Practical SCADA notes
Field-oriented references for HMI/SCADA systems, industrial communication, alarms, tags, historians, and project delivery.
What a Redundant PLC Actually Protects — and How to Commission One
A hot-standby pair earns its cost only if switchover is proven and sync loss is alarmed. What CPU redundancy covers, and testing both directions.
Report-by-Exception in SCADA: Why It Breaks When You Treat It Like Slow Polling
Running report-by-exception and change-of-state — DNP3 events, deadbands, heartbeats, integrity polls — without losing short events or stale values.
The Bypass Nobody Cleared: Making Maintenance Overrides Visible in SCADA
A maintenance bypass is an operating state, not a comment field. Tag naming, ISA-18.2 out-of-service handling, expiry rules, and the audit trail.
Stop Scanning Every SCADA Tag at One Second
Why a flat 1-second scan overloads PLCs and gateways, and how scan classes and load shedding keep the data operators act on fast under stress.
How to Test SCADA Server Switchover Without Fooling Yourself
A green redundancy icon proves the heartbeat works and nothing else. What to check on clients, alarms, historian and background jobs during a failover.
From SCADA Signals to Operational State
How raw SCADA, HMI and protocol values become useful machine state, process state, alarm state and control state, and where each one is decided.
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.
HMI vs SCADA vs MES vs Historian
A field-oriented comparison of common industrial software layers and where their responsibilities overlap.
What is SCADA?
A practical explanation of SCADA systems: what they do, where they fit, and what to watch for on real projects.