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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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Common Control Valve Problems

Common Control Valve Problems

Valves can experience a number of problems, most of them either preventable or repairable. These problems can…


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Problem-solving by Simplification

Problem-solving by Simplification

A whole class of problem-solving techniques focuses on altering the given problem into a simpler form that is…


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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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Level Switches

Level Switches

A level switch is one detecting the level of liquid or solid (granules or powder) in a vessel. Level switches…


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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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Control Valve Actuators

Control Valve Actuators

The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…


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Proximity Switches

Proximity Switches

A proximity switch is one detecting the proximity (closeness) of some object. By definition, these switches…


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Logic Programming in PLCs

Logic Programming in PLCs

Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…


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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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Proportional-only Offset

Proportional-only Offset

A fundamental limitation of proportional control has to do with its response to changes in setpoint and…


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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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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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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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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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Process Flow Diagrams

Process Flow Diagrams

To show a practical process example, let’s examine three diagrams for a compressor control system,…


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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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Safety Instrumented Functions and Systems

Safety Instrumented Functions and Systems

A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…


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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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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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Calibration Errors and Testing

Calibration Errors and Testing

The efficient identification and correction of instrument calibration errors is an important function for…


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What is Hydrostatic Pressure?

What is Hydrostatic Pressure?

A vertical column of fluid generates a pressure at the bottom of the column owing to the action of gravity on…


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Flow Measurement from Differential Pressure

Flow Measurement from Differential Pressure

In our first signal characterization example, we tackle the problem of measuring fluid flow through a pipe. To…


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Valve Positioners

Valve Positioners

The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…


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Techniques for Analyzing Control Strategies

Techniques for Analyzing Control Strategies

Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…


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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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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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Valve Seat Leakage

Valve Seat Leakage

In some process applications, it is important that the control valve be able to completely stop fluid flow…


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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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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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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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Calibration Procedures in Linear, Non-Linear and Discrete Instruments

Calibration Procedures in Linear, Non-Linear and Discrete Instruments

As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…


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Human-Machine Interfaces (HMIs)

Human-Machine Interfaces (HMIs)

Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…


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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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Interposing Relays in PLCs

Interposing Relays in PLCs

In addition to directly performing logic functions, electromechanical relays may also be used as interposing…


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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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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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How Derivatives and Integrals Relate to One Another

How Derivatives and Integrals Relate to One Another

Like many other mathematical operations, the derivative and the integral perform inverse operations from each…


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Null-balance Voltage Measurement

Null-balance Voltage Measurement

A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…


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Flow Switches

Flow Switches

A flow switch is one that detects the flow of some fluid through a pipe. Flow switches often use…


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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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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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Dampers and Louvres

Dampers and Louvres

A damper (otherwise known as a louvre) is a multi-element flow control device generally used to throttle large…


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Safety Instrumented Functions and Systems

Safety Instrumented Functions and Systems

A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…


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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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Overpressure Protection Devices

Overpressure Protection Devices

Fluid pressure exerts force on any surface area it contacts, as described by the formula \(F = PA\). One…


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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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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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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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Variable-area Flowmeters

Variable-area Flowmeters

An variable-area flowmeter is one where the fluid must pass through a restriction whose area increases with…


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Relation Control

Relation Control

A control strategy similar to ratio control is relation control. This is similar to ratio control in that a…


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Valve Positioners

Valve Positioners

The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…


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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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Instrument Turndown (Rangedown)

Instrument Turndown (Rangedown)

An important performance parameter for transmitter instruments is something often referred to as turndown or…


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Understanding the Calculus Concepts of Differentiation and Integration

Understanding the Calculus Concepts of Differentiation and Integration

The following animation shows the calculus concepts of differentiation and integration (with respect to time)…


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Techniques for Analyzing Control Strategies

Techniques for Analyzing Control Strategies

Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…


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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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Vibration Monitoring Hardware

Vibration Monitoring Hardware

The following photograph shows a large air blower in a wastewater treatment facility equipped with a…


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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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The Concept of Integration

The Concept of Integration

Suppose we wished to measure the consumption of propane over time for a large propane storage tank supplying a…


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