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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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Analog Signal Conditioning and Referencing

Analog Signal Conditioning and Referencing

Modern analog-to-digital converters are phenomenally accurate, dependable, repeatable, and surprisingly…


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Understanding the “Normal” Status of a Process Switch

Understanding the “Normal” Status of a Process Switch

Perhaps the most confusing aspect of discrete sensors is the definition of a sensor’s normal status.…


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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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WirelessHART Radio Communication Standard

WirelessHART Radio Communication Standard

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


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Differential (87) Current Protection

Differential (87) Current Protection

One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…


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Relay Circuits and Ladder Diagrams

Relay Circuits and Ladder Diagrams

Electromechanical relays may be connected together to perform logic and control functions, acting as logic…


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Error Corrections

Error Corrections

Abdelaziz, Ahmed (June 2014) Identified numerous typographical errors throughout the book, mostly repeated…


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Introduction to Power System Automation

Introduction to Power System Automation

Those familiar with industrial instrumentation will find much within the electric power industry remarkably…


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Instruction List (IL) Programming

Instruction List (IL) Programming

(Will be addressed in future versions of this book)


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Ladder Diagram (LD) Structure Commands

Ladder Diagram (LD) Structure Commands

The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…


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PID Control Terminology

PID Control Terminology

PID control can be a confusing concept to understand. Here, a brief summary of each term within PID (P. I, and…


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Common Diagnostic Mistakes in Control Systems

Common Diagnostic Mistakes in Control Systems

Volumes could be written about poor diagnostic technique. The following mistakes are not intended to comprise…


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FOUNDATION Fieldbus Function Blocks

FOUNDATION Fieldbus Function Blocks

Data-processing modules within FF systems are known as function blocks. Sometimes these blocks serve merely to…


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LRV and URV Settings, Digital Trim (Digital Transmitters)

LRV and URV Settings, Digital Trim (Digital Transmitters)

The advent of “smart” field instruments containing microprocessors has been a great advance for…


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Indicators, Recorders, Process Switches and Alarms

Indicators, Recorders, Process Switches and Alarms

So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…


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Function Block Diagram (FBD) Programming

Function Block Diagram (FBD) Programming

(Will be addressed in future versions of this book)


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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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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 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 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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Differential (87) Current Protection

Differential (87) Current Protection

One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…


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Antennas and Resonant Circuits (Tank Circuits)

Antennas and Resonant Circuits (Tank Circuits)

Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…


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Filled-bulb Temperature Sensors

Filled-bulb Temperature Sensors

Filled-bulb systems exploit the principle of fluid expansion to measure temperature. If a fluid is enclosed in…


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Instrument and Process Equipment Symbols

Instrument and Process Equipment Symbols

This section shows some of the many instrument symbols found in different types of technical diagrams used to…


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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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Force-balance Pressure Transmitters

Force-balance Pressure Transmitters

An important legacy technology for all kinds of continuous measurement is the self-balancing system. A…


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Pneumatic PID Controllers

Pneumatic PID Controllers

A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…


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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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Continuous Float Level Transmitters

Continuous Float Level Transmitters

Perhaps the simplest form of solid or liquid level measurement is with a float: a device that rides on the…


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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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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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Industrial Instrumentation Summary for Teachers

Industrial Instrumentation Summary for Teachers

To summarize some of the key points and concepts for teaching: Do not waste class time transmitting facts to…


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Thermistors and Resistance Temperature Detectors (RTDs)

Thermistors and Resistance Temperature Detectors (RTDs)

One of the simplest classes of temperature sensor is one where temperature effects a change in electrical…


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Using Manometers for Measuring Pressure

Using Manometers for Measuring Pressure

A very simple device used to measure pressure is the manometer: a fluid-filled tube where an applied gas…


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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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Chemiluminescence Measurement

Chemiluminescence Measurement

Recall that an exothermic chemical reaction is one that releases a net sum of energy, as opposed to an…


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EIA/TIA-232, 422, and 485 Networks

EIA/TIA-232, 422, and 485 Networks

Some of the simplest types of digital communication networks found in industry are defined by the EIA…


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Comparison of  Op-Amp Circuits With Analogous Pneumatic Mechanisms

Comparison of Op-Amp Circuits With Analogous Pneumatic Mechanisms

Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…


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Rotary-stem Valves

Rotary-stem Valves

A different strategy for controlling the flow of fluid is to insert a rotary element into the flow path.…


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Circuit Breakers and Disconnects

Circuit Breakers and Disconnects

Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…


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Thermocouple Types, Junctions, Connector and Tip Styles

Thermocouple Types, Junctions, Connector and Tip Styles

RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…


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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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Proportional-only Control

Proportional-only Control

Imagine a liquid-level control system for a vessel, where the position of a level-sensing float directly sets…


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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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Molecular Quantities

Molecular Quantities

Sample sizes of chemical substances are often measured in moles. One mole of a substance is defined as a…


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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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VSD and VFD Motor Drive Features

VSD and VFD Motor Drive Features

Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…


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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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Kirchhoff’s Current and Voltage Laws

Kirchhoff’s Current and Voltage Laws

Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…


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Chemical Reactor Temperature Control Example

Chemical Reactor Temperature Control Example

Sometimes we encounter a diversity of instrument signal standards in one control system. Such is the case with…


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Error Corrections

Error Corrections

Abdelaziz, Ahmed (June 2014) Identified numerous typographical errors throughout the book, mostly repeated…


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Practical Topic Coverage

Practical Topic Coverage

Nearly every technical course teaches and tests students on definitions, basic concepts, and at least some…


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Metering Pumps

Metering Pumps

A very common method for directly controlling low flow rates of fluids is to use a device known as a metering…


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Concepts and Laws of Probability

Concepts and Laws of Probability

While the term “probability” may evoke images of imprecision, probability is in fact an exact…


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Pneumatic Actuator Response

Pneumatic Actuator Response

A limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…


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Industrial Instrumentation Summary for Teachers

Industrial Instrumentation Summary for Teachers

To summarize some of the key points and concepts for teaching: Do not waste class time transmitting facts to…


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Limit Switches

Limit Switches

A limit switch detects the physical motion of an object by direct contact with that object. An example of a…


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Stoichiometry and the Law of Mass Conservation

Stoichiometry and the Law of Mass Conservation

Stoichiometry is the accounting of atoms before and after a chemical reaction. It is an expression of the Law…


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Polyphase AC Power

Polyphase AC Power

“Polyphase” means “many phases,” describing a form of AC electrical system where…


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