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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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Level Sensor Accessories

Level Sensor Accessories

Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…


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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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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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Introduction to Optical Analysis

Introduction to Optical Analysis

Light is known to interact with matter in very specific ways, which may be exploited as a means of measuring…


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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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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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Distance (21) Protection

Distance (21) Protection

A form of protection against faults on long-distance power lines is called distance relaying, so named because…


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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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Differential Pressure Transmitters

Differential Pressure Transmitters

One of the most common, and most useful, pressure measuring instruments in industry is the differential…


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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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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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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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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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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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Control Valve Characterization

Control Valve Characterization

Control valves are supposed to deliver reliable, repeatable control of process fluid flow rate over a wide…


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Advantages and Disadvantages of Pneumatic Instruments

Advantages and Disadvantages of Pneumatic Instruments

The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…


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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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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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AC Motor Speed Control

AC Motor Speed Control

AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…


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Analyzer Sample Systems

Analyzer Sample Systems

Some analyzers measure the composition of a process stream by directly immersing the sensing element in that…


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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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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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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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Electrical Pressure Elements

Electrical Pressure Elements

Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…


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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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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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Scientific System diagnosis and Scientific Reasoning

Scientific System diagnosis and Scientific Reasoning

At the root of successful system diagnosis is a rigorous adherence to scientific reasoning. There exists no…


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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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Flow Measurement in Open Channels

Flow Measurement in Open Channels

Measuring the flow rate of liquid through an open channel is not unlike measuring the flow rate of a liquid…


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Capacitive Level Measurement

Capacitive Level Measurement

Capacitive level instruments measure electrical capacitance of a conductive rod inserted vertically into a…


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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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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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Sequential Function Chart (SFC) Programming

Sequential Function Chart (SFC) 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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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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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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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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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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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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Vibration Physics

Vibration Physics

One very convenient feature of waves is that their properties are universal. Waves of water in the ocean,…


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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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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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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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Safety Gas Analyzers

Safety Gas Analyzers

Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…


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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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True Mass Flowmeters

True Mass Flowmeters

Many traditional flowmeter technologies respond to the volumetric flow rate of the moving fluid.…


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Auxiliary and Lockout (86) Relays

Auxiliary and Lockout (86) Relays

An important type of “accessory” relay, especially for legacy electromechanical protective relays,…


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References

References

Lipták, Béla G. et al., Instrument Engineers’ Handbook – Process Measurement and Analysis Volume I,…


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Pressure Sensor Accessories

Pressure Sensor Accessories

Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…


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Basics of Electrical Current

Basics of Electrical Current

Current is the name we give to the motion of electric charges from a point of high potential to a point of low…


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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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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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Introduction to Optical Analysis

Introduction to Optical Analysis

Light is known to interact with matter in very specific ways, which may be exploited as a means of measuring…


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On/off Control (Bang-bang Control)

On/off Control (Bang-bang Control)

Once while working as an instrument technician in an aluminum foundry, a mechanic asked me what it was that I…


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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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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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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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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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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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