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Ethernet networks: Repeaters, Cabling and Switching Hubs

Ethernet networks: Repeaters, Cabling and Switching Hubs

An engineer named Bob Metcalfe conceived the idea of Ethernet in 1973, while working for the Xerox research…


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Introduction to Modbus

Introduction to Modbus

Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…


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Digital PID Controllers

Digital PID Controllers

The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…


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Glossary of Cyber-security Terms

Glossary of Cyber-security Terms

Cyber-security seems to have its own vocabulary, ranging from unwieldy technical acronyms to slang terms…


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ANSI/IEEE Function Number Codes

ANSI/IEEE Function Number Codes

In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…


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Ethernet networks: Repeaters, Cabling and Switching Hubs

Ethernet networks: Repeaters, Cabling and Switching Hubs

An engineer named Bob Metcalfe conceived the idea of Ethernet in 1973, while working for the Xerox research…


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Examples of PLC Systems

Examples of PLC Systems

Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…


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What is Internet Protocol (IP)?

What is Internet Protocol (IP)?

I remember first learning about the world-wide Internet, and wondering what it actually looked like. The first…


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Fiber Optic Data Communication

Fiber Optic Data Communication

Light has long been used as a long-range signaling medium. While communication by light through open air is…


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Digital Data Communication Theory

Digital Data Communication Theory

One of the great benefits of digital technology is the ability to communicate vast amounts of information over…


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Motives for Compromising the Security of an Industrial Control System

Motives for Compromising the Security of an Industrial Control System

There are multiple motives for compromising the security of an industrial control system, some of which…


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Open-ended, Shorted and Properly Terminated Transmission Lines

Open-ended, Shorted and Properly Terminated Transmission Lines

Many years ago, when I was first learning about electricity, I happened to discover a length of coaxial…


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Chromatography: Methods, Detectors and Species

Chromatography: Methods, Detectors and Species

Imagine a major marathon race, where hundreds of runners gather in one place to compete. When the starting gun…


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Input/Output (I/O) Capabilities of PLCs

Input/Output (I/O) Capabilities of PLCs

Every programmable logic controller must have some means of receiving and interpreting signals from real-world…


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Supervisory Control

Supervisory Control

In a manually-controlled process, a human operator directly actuates some form of final control element…


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Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)

Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)

At the next OSI Reference Model layer (layer 4) is a set of protocols specifying how reliable communication…


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Design-based Fortifications

Design-based Fortifications

A design-based fortification is one rooted in technical details of system architecture and functionality. Some…


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Policy-based Fortifications

Policy-based Fortifications

These fortifications focus on human behavior rather than system design or component selection. In some ways…


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Basics of Bridge Circuits

Basics of Bridge Circuits

A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…


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Ultrasonic (Sound) Echo Level Measurement

Ultrasonic (Sound) Echo Level Measurement

A completely different way of measuring liquid level in vessels is to bounce a traveling wave off the surface…


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Introduction to Modbus

Introduction to Modbus

Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…


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WirelessHART Radio Communication Standard

WirelessHART Radio Communication Standard

An exciting development in industrial instrumentation is the WirelessHART radio communication standard,…


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The s Variable: Euler’s Relation and Phasor Expressions of Waveforms

The s Variable: Euler’s Relation and Phasor Expressions of Waveforms

A powerful mathematical concept useful for analyzing practically any physical system – electrical…


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Electrical Pressure Elements

Electrical Pressure Elements

Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…


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Fiber Optic Data Communication

Fiber Optic Data Communication

Light has long been used as a long-range signaling medium. While communication by light through open air is…


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Supervisory Control

Supervisory Control

In a manually-controlled process, a human operator directly actuates some form of final control element…


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Ions in Liquid Solutions

Ions in Liquid Solutions

Many liquid substances undergo a process whereby their constituent molecules split into positively and…


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Control Valve Sizing

Control Valve Sizing

When control valves operate between fully open and fully shut, they serve much the same purpose in process…


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Basic Operation of a Gas Chromatograph

Basic Operation of a Gas Chromatograph

This animation shows the basic operation of a gas chromatograph, showing the separation of different molecular…


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Cascade Control

Cascade Control

A simple control system drawn in block diagram form looks like this: Information from the measuring device…


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Pneumatic Sensing Elements

Pneumatic Sensing Elements

Most pneumatic instruments use a simple but highly sensitive mechanism for converting mechanical motion into…


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The Concept of Differentiation

The Concept of Differentiation

Suppose we wished to measure the rate of propane gas flow through a hose to a torch: Flowmeters appropriate…


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Limit, Selector, and Override Controls

Limit, Selector, and Override Controls

Another category of control strategies involves the use of signal relays or function blocks with the ability…


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Digital PID Controllers

Digital PID Controllers

The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…


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Digital Data Communication Theory

Digital Data Communication Theory

One of the great benefits of digital technology is the ability to communicate vast amounts of information over…


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Mechanical Vibration Switches

Mechanical Vibration Switches

A much simpler alternative to continuous vibration sensors (displacement or acceleration) and monitoring…


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The HART Digital/Analog Hybrid Standard

The HART Digital/Analog Hybrid Standard

A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…


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Radio-energy Pulse in Guided-wave Radar Level Measurement

Radio-energy Pulse in Guided-wave Radar Level Measurement

The following animation shows how a radio-energy pulse travels down and then up the waveguide of a guided-wave…


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4 to 20 mA Analog Current Signals

4 to 20 mA Analog Current Signals

The most popular form of signal transmission used in modern industrial instrumentation systems (as of this…


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AC Motor Braking

AC Motor Braking

There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…


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Understanding Area, Volume and Common Geometry

Understanding Area, Volume and Common Geometry

Area refers to the size of two-dimensional surface. Volume refers to the size of a three-dimensional space. To…


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Classical Mechanics

Classical Mechanics

Classical mechanics (often called Newtonian mechanics in honor of Isaac Newton) deal with forces and motions…


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