Controls
SCADA & HMI
Supervisory control, operator interface design, alarm management, and historian data.
Written guides in this section
Full references, procedures, and diagnostic guides published under SCADA & HMI.
SCADA Architecture
The parts of a SCADA system and how data moves between them: I/O servers, the tag database, clients, the historian, the alarm server, and the topologies from a single panel PC to a redundant, distributed plant.
9 min readUpdated Sep 5, 2026
SCADA Servers
What the servers in a SCADA system do and what a utility should expect of them: the I/O, alarm, historian, and client roles, physical versus virtual, redundancy, sizing, placement, backup, patching, licensing, and monitoring.
10 min readUpdated Sep 5, 2026
SCADA Clients
The workstations, browsers, and mobile devices operators use to see and control the system: thick, thin, web, and mobile clients, roles and permissions, where control is allowed from, workstation design, session policy, licensing, and failover behavior.
9 min readUpdated Sep 5, 2026
Historians
What a process historian does that a database does not, how data gets into it, how compression and retrieval work, how to size and keep it, and the settings that quietly throw data away.
8 min readUpdated Sep 5, 2026
Alarm Servers
The part of SCADA that turns a condition into an alarm and manages its life: where detection happens, the alarm state machine, priority, deadband and delays, acknowledgment across clients, the journal, notification, redundancy, timestamps, and flood behavior.
10 min readUpdated Sep 5, 2026
SCADA Communications
How SCADA servers talk to controllers and the field: polling and report by exception, the protocols and what each is for, media from plant Ethernet to radio and cellular, poll rate arithmetic, timeouts and quality, time sync, store and forward, and security.
11 min readUpdated Sep 5, 2026
Topics in this area
SCADA Fundamentals
What a SCADA system is made of and how the pieces relate.
8 topics
HMI Design
Building operator displays people can actually run a plant from.
8 topics
Alarm Management
Making an alarm system that operators trust instead of silence.
8 topics
Historian & Data
Collecting, compressing, and retrieving process history.
7 topics
Platforms
Platform notes. Vendor names are used for identification only.
7 topics
Troubleshooting
What to check when the screen stops matching the plant.
8 topics
Direct contact
Have a controls question?
Reach Eric Sullivan directly about anything on this site, a controls or automation topic, or one of his personal projects.
References to manufacturers, products, model numbers, software platforms, technical specifications, companies, standards organizations, or other organizations are provided for informational purposes and do not imply sponsorship, endorsement, authorization, or affiliation unless expressly stated. Manufacturer specifications must be independently verified against current manufacturer documentation.