How SCADA Systems Work

Section 2: How SCADA Systems Work
A SCADA system performs four functions:
1. Data acquisition
2. Networked data communication
3. Data presentation
4. Control
These functions are performed by four kinds of SCADA components:
1. Sensors (either digital or analog) and control relays that
directly interface with the managed system.
2. Remote telemetry units (RTUs). These are small computerized
units deployed in the field at specific sites and locations.
RTUs serve as local collection points for gathering reports
from sensors and delivering commands to control relays.
3. SCADAmaster units. These are larger computer consoles that
serve as the central processor for the SCADA system. Master
units provide a human interface to the system and automatically
regulate the managed system in response to sensor inputs.
4. The communications network that connects the SCADA
master unit to the RTUs in the field.
The World’s Simplest SCADA System
The simplest possible SCADA system would be a single circuit
that notifies you of one event. Imagine a fabrication machine that
produces widgets. Every time the machine finishes a widget, it
activates a switch. The switch turns on a light on a panel, which
tells a human operator that a widget has been completed.
Obviously, a real SCADA system does more than this simple
model. But the principle is the same. A full-scale SCADA system
just monitors more stuff over greater distances.
Let’s look at what is added to our simple model to create a fullscale
SCADA system:
SCADA Tutorial • DPS Telecom • 4955 East Yale Avenue, Fresno, CA 93727 • (800) 622-3314 • Fax (559) 454-1688 • www.dpstelecom.com

This RTU Grows with
Your Network
When you’re planning your SCADA
systems, think about the future. You
don’t want to get locked into a system
that’s inadequate for your future needs
— but you don’t want to spend too
much for alarm capacity you won’t
immediately use, either.
The NetGuardian 832A remote
telemetry unit expands its capacity as
your needs change. Install a
NetGuardian at your remote site now,
and get exactly the right coverage for
your current needs.
Then, as your remote site grows, you
can extend your alarm monitoring
capabilities by adding NetGuardian
DX Expansion units. Each
NetGuardian DX adds 48 more alarm
points, and you can daisy-chain up to
three NetGuardian DXs off each
NetGuardian 832A base unit.
Unit Capacity
Base NG 832 32
1 DX 80
2 DX 128
3 DX 176
NetGuardian DX: Expand your alarm monitoring
capacity with NetGuardian DX
Expansion Units.