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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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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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WirelessHART Radio Communication Standard

WirelessHART Radio Communication Standard

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


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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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Motives for Compromising the Security of an Industrial Control System

Motives for Compromising the Security of an Industrial Control System

There are multiple motives for compromising the security of an industrial control system, some of which…


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Introduction to Modbus

Introduction to Modbus

Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…


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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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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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How to Teach Yourself PLC Programming

How to Teach Yourself PLC Programming

Learning PLC programming is a very important skill. If your job involves programming, then you will likely…


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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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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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Sequential Function Chart (SFC) Programming

Sequential Function Chart (SFC) Programming

(Will be addressed in future versions of this book)


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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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On/off Electric Motor Control Circuits

On/off Electric Motor Control Circuits

An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…


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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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Instruction List (IL) Programming

Instruction List (IL) Programming

(Will be addressed in future versions of this book)


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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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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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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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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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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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Vibration Sensors

Vibration Sensors

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


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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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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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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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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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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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Weight-based Level Measurement

Weight-based Level Measurement

Weight-based level instruments sense process level in a vessel by directly measuring the weight of the vessel.…


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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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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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On/off Electric Motor Control Circuits

On/off Electric Motor Control Circuits

An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…


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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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What is Internet Protocol (IP)?

What is Internet Protocol (IP)?

I remember first learning about the world-wide Internet, and wondering what it actually looked like. The first…


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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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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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Principles, not Procedures

Principles, not Procedures

One of the marks of a successful problem-solver is a habit of applying general principles to every new problem…


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Pneumatic Sensing Elements

Pneumatic Sensing Elements

Most pneumatic instruments use a simple but highly sensitive mechanism for converting mechanical motion into…


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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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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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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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Circuit Failure Analysis

Circuit Failure Analysis

Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose…


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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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AC Motor Braking

AC Motor Braking

There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…


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Active Reading and Outlining Documentation

Active Reading and Outlining Documentation

Learning from reading printed text is a kind of problem-solving activity it is own right. The problem is how…


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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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Non-contact Temperature Sensors

Non-contact Temperature Sensors

Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…


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Split-Range Control

Split-Range Control

There are many process control applications in the industry where it is desirable to have multiple control…


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Policy-based Fortifications

Policy-based Fortifications

These fortifications focus on human behavior rather than system design or component selection. In some ways…


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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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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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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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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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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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Different PID Equations

Different PID Equations

For better or worse, there are no fewer than three different forms of PID equations implemented in modern PID…


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Change-of-quantity Flow Measurement

Change-of-quantity Flow Measurement

Flow, by definition, is the passage of material from one location to another over time. So far this chapter…


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References

References

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


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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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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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WirelessHART Radio Communication Standard

WirelessHART Radio Communication Standard

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


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