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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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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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Supervisory Control

Supervisory Control

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


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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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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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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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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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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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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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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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WirelessHART Radio Communication Standard

WirelessHART Radio Communication Standard

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


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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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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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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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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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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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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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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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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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Material Volume Measurement

Material Volume Measurement

A variety of technologies exist to measure the quantity of stored material in a vessel. For liquid…


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Functional Diagrams: the Flow of Information within a Control System

Functional Diagrams: the Flow of Information within a Control System

A unique form of technical diagram for describing the abstract functions comprising a control system (e.g. PID…


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Instrument Identification Tags

Instrument Identification Tags

Up until this point, we have explored various types of instrumentation diagram, each one making reference to…


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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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Pilot Valves and Pneumatic Amplifying Relays

Pilot Valves and Pneumatic Amplifying Relays

Self-balancing mechanisms consisting solely of a baffle/nozzle detector coupled to a feedback bellows, while…


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Understanding Electrical Power Grids

Understanding Electrical Power Grids

The term “grid” refers to the conductors and equipment interconnecting power sources to power…


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Digital Multimeter (DMM) Tips and Tricks

Digital Multimeter (DMM) Tips and Tricks

The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…


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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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What are Simple Machines?

What are Simple Machines?

A machine in the broad sense of the word is any device designed to translate some form of energy into useful…


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Practical PID Controller Features

Practical PID Controller Features

In order for any PID controller to be practical, it must be able to do more than just implement the PID…


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Temperature Switches

Temperature Switches

A temperature switch is one detecting the temperature of some substance. Temperature switches often use…


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Formulae for Common Chemical Compounds

Formulae for Common Chemical Compounds

Most of these formulae appear in molecular chemical form rather than structural form. For example, ethanol…


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Solenoid Valves

Solenoid Valves

A very common form of on/off valve used for pneumatic and hydraulic systems alike is the solenoid valve. A…


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4-wire “Passive” Versus “Active” Output Transmitters

4-wire “Passive” Versus “Active” Output Transmitters

Some self-powered (4-wire) analog electronic transmitters are designed to behave as electrical loads rather…


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The Difference Between Series and Parallel Circuits

The Difference Between Series and Parallel Circuits

In addition to Ohm’s Law, we have a set of rules describing how voltages, currents, and resistances…


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Feedforward Control

Feedforward Control

“Feedforward” is a rather under-used control strategy capable of managing a great many types of…


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Energy in Chemical Reactions

Energy in Chemical Reactions

A chemical reaction resulting in a net release of energy is called exothermic. Conversely, a chemical reaction…


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Phasor Analysis of Transformer Circuits

Phasor Analysis of Transformer Circuits

Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…


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Sliding-stem Valves

Sliding-stem Valves

A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…


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Unit Conversions and Physical Constants

Unit Conversions and Physical Constants

Converting between disparate units of measurement is the bane of many science students. The problem is worse…


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Standardized Volumetric Flow

Standardized Volumetric Flow

The majority of flowmeter technologies operate on the principle of interpreting fluid flow based on the…


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Basics of pH Measurement in Industrial Control

Basics of pH Measurement in Industrial Control

Hydrogen ion activity in aqueous (water-solvent) solutions is a very important parameter for a wide variety of…


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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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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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Actuator Bench-set

Actuator Bench-set

Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…


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Pressure-based Flowmeters

Pressure-based Flowmeters

All masses require force to accelerate (we can also think of this in terms of the mass generating a reaction…


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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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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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Practical PID Controller Features

Practical PID Controller Features

In order for any PID controller to be practical, it must be able to do more than just implement the PID…


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Process/Instrument Suitability

Process/Instrument Suitability

Every flow-measuring instrument exploits a physical principle to measure the flow rate of fluid stream.…


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Transfer Function Analysis

Transfer Function Analysis

An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…


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Flow Measurement from Differential Pressure

Flow Measurement from Differential Pressure

Take for instance the problem of measuring fluid flow through a pipe. To the layperson, this may seem to be a…


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Numerical Integration

Numerical Integration

As we have seen, the concept of integration is finding the accumulation of one variable multiplied by another…


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Sequential Function Chart (SFC) Programming

Sequential Function Chart (SFC) Programming

(Will be addressed in future versions of this book)


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Memory Maps and I/O Addressing

Memory Maps and I/O Addressing

A wise PLC programmer once told me that the first thing any aspiring programmer should learn about the PLC…


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Conservation Laws

Conservation Laws

The Law of Mass Conservation states that matter can neither be created nor destroyed. The Law of Energy…


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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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High-reliability Control Systems

High-reliability Control Systems

As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…


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Pressure Switches

Pressure Switches

A pressure switch is one detecting the presence of fluid pressure. Pressure switches often use diaphragms or…


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The Stuxnet Virus

The Stuxnet Virus

In November of 2007 a new computer virus was submitted to a virus scanning service. The purpose of this new…


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