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HMI and SCADA

The layer above the PLC: HMI screen and alarm design, SCADA architecture, historians, tag databases and the protocols that carry plant data to the control room.

An HMI is the operator's window onto one machine; SCADA is the supervisory layer over many. The distinction matters when you are specifying a system, and it matters even more when you are designing alarms, because the most common failure in this layer is not a technical one, it is a nuisance-alarm flood that trains operators to ignore the screen.

16 articles in this hub

Flat vector diagram of a SCADA remote access architecture showing a laptop connecting through a VPN tunnel and dual firewalls to a SCADA server and PLC rack in a segmented OT network
scadaremote accesscybersecurity

SCADA Remote Access: How to Do It Safely

Remote access to SCADA systems is unavoidable in modern plants, but done wrong it is a direct path to a breach. Here is how to set it up safely.

Jul 23, 20269 min read

Flat vector diagram of an HMI screen displaying a prioritised alarm list connected to a PLC rack and tag database, illustrating HMI alarm configuration workflow
hmi programmingalarm managementhmi configuration

HMI Alarm Configuration: From Raw Bit to Useful Alert

Learn how to configure HMI alarms correctly: priority levels, deadbands, acknowledgment workflows and the display rules that separate useful alerts from alarm floods.

Jul 23, 20269 min read

HMI tag linking diagram showing PLC address mapping between touchscreen and PLC rack
hmi programmingtag mappingplc addressing

HMI Tag Linking: Mapping PLC Addresses Correctly

HMI tag linking connects your screen objects to real PLC memory. Get the data type, polling rate or address wrong and your display lies to you. Here is how to do it right.

Jul 11, 20267 min read

SCADA historian data logging architecture diagram showing PLC tags flowing into a time-series database and trend display
scadahistoriandata logging

SCADA Historian: How Process Data Gets Logged

A SCADA historian is not just a database. Learn how process historians compress, store and serve time-series plant data, and how to choose the right one.

Jul 10, 20268 min read

HMI screen design best practices showing three operator interface panels with process mimics and alarm indicators
hmiscreen designoperator interface

HMI Screen Design: Practical Rules That Work

Good HMI screen design is not about aesthetics. It's about operators making correct decisions fast. Here's what actually works on the plant floor.

Jul 10, 20269 min read

SCADA alarm management dashboard showing alarm severity bands and nuisance alarm reduction workflow
scadaalarm managementisa-18.2

SCADA Alarm Management: Cutting Nuisance Alarms the Right Way

Nuisance alarms erode operator trust and hide real faults. Here is how to audit, rationalise and configure SCADA alarms using ISA-18.2 and EEMUA 191 benchmarks.

Jul 7, 20269 min read

SCADA communication protocols Modbus DNP3 and OPC UA flat vector diagram showing RTU to SCADA server connections
scadaprotocolsopc ua

SCADA Communication Protocols: Modbus, DNP3 and OPC UA

Modbus, DNP3 and OPC UA each solve a different problem in SCADA. This guide breaks down how each works, where it fits, and what trips engineers up in the field.

Jul 6, 20269 min read

SCADA software architecture diagram showing dashboard, PLCs, RTUs and historian connections
scadahmiindustrial software

What Is SCADA Software? Features and How to Choose One

SCADA software turns raw field data into actionable plant visibility. Here is what it actually does, which features separate good platforms from frustrating ones, and how to choose.

Jul 6, 20268 min read

SCADA network design diagram showing field bus, control network and enterprise layers with firewalls and managed switches
scadanetworkingcybersecurity

SCADA Network Design: Topologies, Protocols and Security

SCADA network design covers topology choices, protocol selection and cybersecurity hardening. Get the real engineering decisions right the first time.

Jul 6, 20269 min read

SCADA control system hierarchy diagram showing PLC, RTU, SCADA server and operator workstation layers
scadacontrol systemsautomation

SCADA Control System Basics for Automation Engineers

SCADA control systems sit above the PLC but below the enterprise network. Here's how the layers connect, what software does the work, and where things go wrong.

Jul 5, 20269 min read

HMI and SCADA architecture diagram showing PLC, local HMI and SCADA workstation layers in a plant
hmiscadaplant architecture

HMI and SCADA: How They Fit Together in a Real Plant

HMI and SCADA are not interchangeable terms. Learn how each layer works, where they connect, and how a real plant ties them together from sensor to supervisor.

Jul 5, 20269 min read

SCADA system architecture diagram showing three layers: field devices, RTUs and PLCs, and master station
scadartumaster station

SCADA System Architecture: Layers, RTUs and the Master Station

Understand SCADA system architecture in depth: the three-layer model, how RTUs and PLCs differ, what the master station really does, and how modern IP networks changed everything.

Jul 5, 20269 min read

SCADA vs PLC architecture diagram showing PLC control layer and SCADA supervisory layer connected over Ethernet
scadaplcindustrial automation

SCADA vs PLC: How They Work Together on the Plant Floor

SCADA and PLCs are not competitors. One controls the process, the other watches it. This guide breaks down the real roles, how they communicate, and where engineers get the split wrong.

Jul 4, 20268 min read

SCADA system architecture diagram showing PLCs, RTUs, network layer and SCADA server with HMI screens
scadahmiindustrial automation

What Is a SCADA System and How Does It Work?

SCADA stands for Supervisory Control and Data Acquisition. Learn what a SCADA system actually does, how its components connect, and where it fits with PLCs and HMIs.

Jun 28, 20267 min read

HMI programming in TIA Portal showing screen layouts connected to PLC tags with alarm indicators
hmi programmingtia portalsiemens

HMI Programming in TIA Portal: A Practical Guide

Learn HMI programming in TIA Portal: how to build screens, connect PLC tags, configure alarms and wire up navigation buttons that actually work in production.

Jun 28, 20269 min read

SCADA vs HMI architecture diagram showing local HMI panel connected to single PLC and SCADA server connected to multiple PLCs across a plant
scadahmiindustrial automation

SCADA vs HMI: What Actually Differs and Why It Matters

SCADA and HMI are not the same thing, even though vendors blur the line constantly. Learn the real architectural difference with concrete examples.

Jun 28, 20267 min read