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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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Fluid Mechanics

Fluid Mechanics

A fluid is any substance having the ability to flow: to freely change shape and move under the influence of a…


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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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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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Teaching Technical Practices (Labwork)

Teaching Technical Practices (Labwork)

Labwork is an essential part of any science-based curriculum. Here, much improvement may be made over the…


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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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Instantaneous and Time-overcurrent (50/51) Protection

Instantaneous and Time-overcurrent (50/51) Protection

Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…


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Electrical Signal and Control Wiring

Electrical Signal and Control Wiring

There is much to be said for neatness of assembly in electrical signal wiring. Even though the electrons…


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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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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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Classified Areas and Electrical Safety Measures

Classified Areas and Electrical Safety Measures

Any physical location in an industrial facility harboring the potential of explosion due to the presence of…


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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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Electrical Sensors: Potential Transformers (PTs) and Current Transformers (CTs)

Electrical Sensors: Potential Transformers (PTs) and Current Transformers (CTs)

The two “process variables” we rely on most heavily in the field of electrical measurement and…


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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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Ladder Diagram (LD) Programming Contacts and Coils

Ladder Diagram (LD) Programming Contacts and Coils

In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…


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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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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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Legal Code

Legal Code

Creative Commons Attribution 4.0 International Public License By exercising the Licensed Rights (defined…


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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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Introduction to Protective Relaying

Introduction to Protective Relaying

Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…


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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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Self-balancing Pneumatic Instruments Principles

Self-balancing Pneumatic Instruments Principles

A great many precision instruments use the principle of balance to measure some quantity. Perhaps the simplest…


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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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Laminar Flowmeters

Laminar Flowmeters

A unique form of differential pressure-based flow measurement deserves its own section in this flow…


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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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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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Radiation Level Measurement

Radiation Level Measurement

Certain types of nuclear radiation easily penetrates the walls of industrial vessels, but is attenuated by…


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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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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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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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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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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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Interconnected Generators

Interconnected Generators

Any power grid large enough to meet the demand of an entire nation must have multiple generators drawing from…


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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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Fluid Mechanics

Fluid Mechanics

A fluid is any substance having the ability to flow: to freely change shape and move under the influence of a…


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Elementary Thermodynamics

Elementary Thermodynamics

Thermodynamics is the study of heat, temperature, and their related effects in physical systems. As a subject,…


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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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Structured Text (ST) Programming

Structured Text (ST) Programming

(Will be addressed in future versions of this book)


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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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Root Mean Square (RMS) Quantities

Root Mean Square (RMS) Quantities

It is often useful to express the amplitude of an alternating quantity such as voltage or current in terms…


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A Comparison of PID Controller Tuning Techniques

A Comparison of PID Controller Tuning Techniques

In this section I will show screenshots from a process loop simulation program illustrating the effectiveness…


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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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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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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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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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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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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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Positive Displacement Flowmeters

Positive Displacement Flowmeters

A positive displacement flowmeter is a cyclic mechanism built to pass a fixed volume of fluid through with…


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Valve Packing

Valve Packing

Regardless of valve type, all stem-actuated control valves require some form of seal allowing motion of the…


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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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Zero and Span Adjustments (Analog Instruments)

Zero and Span Adjustments (Analog Instruments)

Linearity of Measurement Instruments The purpose of calibration is to ensure the input and output of an…


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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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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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An Analogy for Calibration Vs Ranging

An Analogy for Calibration Vs Ranging

The concepts of calibration (trimming) and ranging are often difficult for new students of instrumentation to…


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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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Hand Switches and Stackable Switches

Hand Switches and Stackable Switches

A hand switch is exactly what the name implies: an electrical switch actuated by a person’s hand motion.…


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Directional Overcurrent (67) Protection

Directional Overcurrent (67) Protection

While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…


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Colorimetric and Potentiometric pH Measurement

Colorimetric and Potentiometric pH Measurement

pH is the measurement of the hydrogen ion activity in a liquid solution. It is one of the most common forms of…


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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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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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