ICS/SCADA Terms.
Servers
Used to store configuration for the ICS and saves process data in historians for later retrieval. The servers connect to business networks to allow remote operations, configuration, or information exchanges to improve productivity.
Engineering Workstations
A specializ...
Used to store configuration for the ICS and saves process data in historians for later retrieval. The
servers connect to business networks to allow remote operations, configuration, or information
exchanges to improve productivity.
Engineering Workstations
A specialized type of HMI, typically interface with the servers to modify the database or controllers
to ensure the critical process runs properly. As we gain an understanding of the similarities between
IT and ICS architectures, we will have greater success mapping traditional cybersecurity issues into
the ICS domain.
Field Devices
The instruments and sensors that measure process parameters and the actuators that control the
process. This is the interface between the ICS and the physical process, be it the mixing of chemicals,
the management of trains, or measuring of pressures in a gas pipeline. This is the point in the system
where information is collected about the process, modifications are made, and the process is
controlled. The sensors or measuring instruments are often referred to as input devices because
they "input" data into the ICS. In contrast, switches, valves, and other types of actuators that control
the process are called output devices. This input and output information is often referred to as I/O.
Safety Systems
Safety systems provide protection to the process, physical equipment, or people from harmful
situations that may arise during operations. It is a counter action critical in industrial operations in
the case of a process goes beyond allowable control parameters. While this would result in a loss of
productivity, it would spare the equipment and people harm. Safety systems are traditionally,
designed to be separated from the control systems they protect. However, they frequently share
some communications, field devices, alarms, etc.
Human-Machine Interface (HMI)
The user interface in a manufacturing or process control system. It provides a graphics-based
visualization of an industrial control and monitoring system. Previously called an "MMI" (man-
machine interface), an HMI typically resides on a computer that communicates with a specialized
computer in the plant, such as a programmable automation controller (PAC), programmable logic
controller (PLC) or remote terminal unit (RTU). The HMI generally comes in two forms: either a touch
panel or a software-based application that is loaded on a personal computer, workstation, tablet, or
smart phone.
ICS Component - Relationship
Machines installed in industrial plants use a variety of field devices for control and monitoring. These
devices connect to field controllers, which connect to Human Machine Interface (HMI). Notice the
communication flow of the devices to each other. We will examine each of these segments in-depth
on the following pages.
Sensor Types
, Discrete, Analog, Digital
Input - Discrete
Discrete input sensors support binary events including alarms and states. For example, the tank is
full, the door is closed, the pressure is too high, or the pump is turned on.
Input - Analog
Analog input sensors (transmitters) measure continuous processes such as flow, level, or pressures
within a range; 0-100%, empty to full, 0 to 100 mph. Typically, they transmit this information to field
controllers using an analog signal such as a 4 to 20-mA.
Input - Digital
Digital input sensors are similar to both discrete and analog instruments in that they measure
continuous processes (such as flows) and support binary events. However, instead of using an analog
loop signal or clean contacts, digital sensors use a digitally encoded ICS communications protocol
format (representing an equivalent to 1s and 0s) signal to relay the data.
Output - Discrete
Like their input counterpart, discrete output devices are also binary appliances. For instance, the
field controller issues a signal to an output device, such as a circuit breaker, to open or close a
breaker. Discrete output devices can communicate directly with discrete input devices. Furthermore,
they can make control decisions and are programmable like a field controller.
Output - Analog
The analog output transmits analog signals (voltage or current) that operate controls. Analog
outputs are predominantly used to control actuators, valves, and motors in industrial environments.
In this case, the field controller will send a varying electrical signal that can open or close the valve as
needed.
Output - Digital
A digital output allows you to control a voltage with a computer. If the computer instructs the
output to be high, the output will produce a voltage (generally about 5 or 3.3 volts). If the computer
instructs the output to be low, it is connected to ground and produces no voltage. As a result, they
can communicate more quickly and reliably, thus enabling their use in environments that are more
critical, covering a wider range of applications. Examples include: alarms, control relays, fans, lights,
horns, valves, switches, motor starters, etc.
A control loop, single-loop control
is the fundamental building block of industrial control systems. It is communication used to regulate
the process. It consists of a group of components working together as a system to achieve and
maintain a desired value of a system variable by manipulating the value of another variable in the
control loop.
RS232
which is an older technology in the IT domain, is still commonly used for point-to-point
communications in RTUs and PLCs.
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