What is scada? Definition and Details paessler com/it-explained/scada it explained: scada back to index Content

How does SCADA work?

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SCADA levels
There are five levels or hierarchies in traditional SCADA architecture. SCADA levels are
based on Purdue Enterprise Reference Architecture, a reference model for enterprise
architecture. These levels illustrate how the components of a typical SCADA system are
related to each other.
Level 0, at the bottom of the technology stack, comprises the low-level remote field
devices like sensors from which data is acquired.
Level 1 concerns inputs and outputs and consists of field device controllers like
programmable logic controllers (PLCs), intelligent electronic (or end) devices (IEDs), and
remote terminal (or telemetry) units (RTUs) that connect via interfaces with remote field
devices.
Level 2 includes supervisory computers that manage inputs and outputs from and to field
device controllers, update one or more databases, connect via interfaces with external
systems, and provide data for visualization on HMIs at a centralized control hub.
Level 3 is concerned with communications and production control and is the level at
which data from level 2 is transmitted to the SCADA control hub.
Level 4, the SCADA control hub, is the production scheduling level or business network
level and includes HMIs which are used by human operators like technicians and data
analysts. At level 4, managers and administrators may adjust production throughput and
monitor inventory and logistics.
SCADA points
A setpoint is the target value for a variable, for example a temperature that a piece of
equipment must not exceed. SCADA points are monitored inputs and outputs. An
example of a hard point is a temperature. An example of a soft point is the result of a
calculation or event(s). SCADA point logs help operators to troubleshoot system
problems like identifying the state of different points at the time a machine failed.