Articles
Field-oriented references for HMI/SCADA systems, industrial communication, alarms, tags, historians, and project delivery.
Real captures of the three ways a Select gets no usable answer — silence, mismatched SystemBytes, and a wrong SessionID — and the SEMI E37 timers T5, T6 and T7 that decide what your log shows.
How IEC 62439-3 PRP and HSR deliver bumpless redundancy for SCADA and IEC 61850, why a failed LAN goes unnoticed, and what to monitor at commissioning.
Changing ladder logic in a running PLC safely: online edit versus download, scan-order traps, seal-in glitches, forces, and a pre-edit checklist.
Commissioning a serial-to-Ethernet device server carrying Modbus RTU: operating mode, packing timers, TCP framing, idle timeouts and half-duplex control.
A Modbus TCP-to-RTU gateway can answer ping and still drop requests. Finding the queue saturation behind stale tags, and tuning the driver for it.
Making an HMI screen state its own identity: ISA-101.01 display hierarchy as the breadcrumb skeleton, command labels that show scope, and testing copied screens.
A sequence screen showing only a step number sends the operator hunting across four displays. Separate state, step, and hold reason, and latch the reason.
Popup context passing for reusable faceplates: one stable equipment key, command binding that fails closed, and telling a broken binding from bad quality.
Recording calibration, manual mode and bypass windows as event records separate from the sampled stream, joined back by asset ID and time window.
Modbus TCP devices cap simultaneous connections lower than you think. Inventorying clients, reading real socket behaviour, and protecting the HMI.
How a mishandled transaction ID lets a Modbus TCP gateway hand your SCADA driver the wrong register's value — and how to prove it with a capture.
Using StatusCode severity bits, SourceTimestamp and ServerTimestamp to catch frozen data, cached gateway values and clock drift a value-only HMI hides.
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.
Rework quietly breaks linear MES route models. How to bind visit numbers, dispositions, and equipment events to the right route step instance.
Historians key archive data to a point ID or a name string, so a rename can split a tag's history in two. What to verify before operators find the gap.
The host wrote the EC, the tool returned EAC = 0, and nine lots ran on the old value. SEMI E5 EAC codes, a real S2F13 readback on the wire, the S2F29 namelist, and the SAT matrix.
A failed transmitter pegs a tag at full scale for eleven hours. Correcting the record with an audit trail that survives review, raw sample intact.
The shift report says 1,738 good parts and the HMI says 1,742. Where to look first: counter style, historian deltas, S6F11 event time, or the spool.
Commissioning a Modbus RTU link the right way: prove polarity, termination, biasing and grounding before you ever open the register map.
Commissioning OPC UA Alarm & Condition subscriptions: event filters, the Retain flag, ConditionRefresh, and the failures that appear on reconnect.
A green redundancy icon proves the heartbeat works and nothing else. What to check on clients, alarms, historian and background jobs during a failover.
Averaging old process data hides trips and flattens peaks. Classifying tags, picking a method per class, and testing a purge job before production.
Why setpoint entry fails on the acknowledgment path, splitting display limits from PLC hard limits, and the tests that catch silent rounding.
A staged plan for rotating MQTT broker, client and CA certificates without breaking publishers, store-and-forward queues or Sparkplug birth sequences.
How OPC UA separates certificate trust, user identity and Part 18 role mapping — and commissioning writes so the wrong session can't move a setpoint.
A forced valve and a substituted flow reading are different overrides, and one Manual bit can't tell them apart. Logging that survives a server restart.
The Modbus unit identifier is 'useless' on TCP until a gateway is involved. How routing works behind serial gateways, and finding the slave that answered.
How reverse connect flips the TCP direction through a cell firewall, and the certificate, endpoint and diagnostic traps that still bite afterward.
Running a restore drill: what falls out of the backup set, the OPC UA certificate traps, RPO and retention per artefact, and a measured RTO against the target.
Nobody memorizes a service account password, so a 90-day policy buys little. What IEC 62443-3-3 SR 1.2 and NIST 800-63B actually ask for.
Event frames pay off only if their boundaries hold. Where to take start and end triggers, what to capture as attributes, and frames that never close.
Where lot traceability breaks when built from equipment events: missing lot context, GEM event time, spool replay order, and split/merge genealogy.
Store-and-forward hands you hours-old samples when a link recovers. Which timestamp wins, what a late value may overwrite, and how to mark it.
After a PLC download the session opens and every item returns Bad_NodeIdUnknown. How namespace indexes and client caches shift, and what to check first.
Running alarm rationalization sessions that produce usable priorities, causes and operator response guidance instead of another unread spreadsheet.
Designing downtime reason codes operators pick correctly under pressure: prompt timing, auto-coding from PackML state, and the fields reports need.
Using Last Will, birth messages and retained state so a SCADA screen shows offline, stale and healthy as three things — not one green icon that lies.
Picking historian deadbands and compression from the instrument and the process, not HMI decimal places, so trends keep movement without storing noise.
Mode is who may command the equipment; state is what it is doing. SEMI E30's control state model splits them — here is how to split the HMI to match.
Project notes about naming, alarms, screenshots, networking, commissioning, backups, and documentation habits that matter later.
Laying out Sparkplug B group, edge node and device IDs — plus birth certificates, aliases and STATE — so a rename doesn't break every subscription.
A practical checklist for designing HMI faceplates that operators can use quickly, consistently, and safely during normal operation and troubleshooting.
A field checklist for commissioning managed industrial Ethernet switches used by SCADA servers, PLCs, remote I/O, drives, cameras, and protocol gateways.
A commissioning checklist for validating HMI and SCADA screens, tags, alarms, trends, historians, users, backups and comms paths before handover.
A practical guide for creating readable, maintainable SCADA tag names across equipment, signals, alarms, trends, and reports.