Learning outcomes
- Explain the key principles of scada architecture and tag databases.
- Carry out a structured practical check or configuration task.
- Recognise common faults, risks and evidence needed for diagnosis.
Module 12 · Lesson 1
SCADA architecture and tag databases
Understand clients, servers, I/O servers, historians, redundancy, tags, quality and update rates.
Before you begin
SCADA architecture diagram and development environment.
Safety: Use site procedures, approved test equipment and competent supervision. Never bypass a protection or interlock without formal control.
Step-by-step learning
- Trace one tag from field instrument through PLC, communications driver and SCADA object.
- Define tag naming, data type, engineering units, quality and update rate.
- Separate control, status, alarm and calculated tags.
- Document server roles, dependencies and failover paths.
Ian's practical tips:
- A beautiful graphic built on a poor tag database becomes expensive technical debt.
- Quality and timestamp should travel with the value wherever possible.
Fault-finding questions
- What should be happening, and what evidence proves it?
- Where is the last known correct signal, voltage, state or process condition?
- What changed immediately before the fault?
- Can the system be divided into smaller testable sections?
Practical activity
Create a one-page test record for this lesson. Include expected values, measured results, equipment used, risks controlled, defects found and the final proven condition.