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Bi-metal Temperature Sensors

Bi-metal Temperature Sensors

Solids tend to expand when heated. The amount that a solid sample will expand with increased temperature…


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Electrical Sources and Electronic Load

Electrical Sources and Electronic Load

By definition, a source is a device delivering energy into a system, while a load is a device extracting…


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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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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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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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Phasors, Phase Shift and Phasor Algebra

Phasors, Phase Shift and Phasor Algebra

Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…


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P, I, and D Responses Graphed

P, I, and D Responses Graphed

Visualizing the actions of P, I, and D tuning parameters using graphs is extremely useful in predicting the…


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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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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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Laminar Flowmeters

Laminar Flowmeters

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


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Teaching Technical Theory

Teaching Technical Theory

Learning is not merely a process of information transfer. It is first and foremost a transformation of…


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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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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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Self-regulating, Integrating, and Runaway Process Characteristics

Self-regulating, Integrating, and Runaway Process Characteristics

Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…


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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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Gas Filter Correlation (GFC) Spectroscopy

Gas Filter Correlation (GFC) Spectroscopy

Using filter cells to eliminate wavelengths associated with interfering gases is called positive filtering in…


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Digital Representation of Text

Digital Representation of Text

Binary patterns are not just able to represent numerical values. Given a standardized code, they may represent…


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Troubleshooting Current Loops

Troubleshooting Current Loops

A fundamental principle in instrumentation system troubleshooting is that every instrument has at least one…


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Diagnosing Feedback Control Problems

Diagnosing Feedback Control Problems

Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…


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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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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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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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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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Dispersive Spectroscopy

Dispersive Spectroscopy

The dispersion of visible light into its constituent colors goes all the way back to the 17th century with…


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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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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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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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Supervisory Control

Supervisory Control

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


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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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Vibration Sensors

Vibration Sensors

Sensors used to measure vibration come in three basic types: displacement, velocity, and acceleration.…


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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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FOUNDATION Fieldbus Design Philosophy

FOUNDATION Fieldbus Design Philosophy

To understand just how different FOUNDATION Fieldbus is from other digital instrument systems, consider a…


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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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Gas Filter Correlation (GFC) Spectroscopy

Gas Filter Correlation (GFC) Spectroscopy

Using filter cells to eliminate wavelengths associated with interfering gases is called positive filtering in…


Textbook

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.…


Textbook

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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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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Mathematical Problem-solving Techniques

Mathematical Problem-solving Techniques

Some problem-solving techniques are unique to quantitative problems, involving mathematical calculations. In…


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Loop Diagrams (Loop Sheets)

Loop Diagrams (Loop Sheets)

Finally, we arrive at the loop diagram (sometimes called a loop sheet) for the compressor surge control system…


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Analog to Digital Conversion and ADCs

Analog to Digital Conversion and ADCs

In order to provide an interface between the internal (digital) world of a computer and the external (analog)…


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