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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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Pressure Sensor Accessories

Pressure Sensor Accessories

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


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Temperature Sensor Accessories

Temperature Sensor Accessories

One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…


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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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Analog Electronic PID Controllers

Analog Electronic PID Controllers

Constructing PID control systems using discrete components is a fairly simple method involving operational…


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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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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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Velocity-based Flowmeters

Velocity-based Flowmeters

The Law of Continuity for fluids states that the product of mass density (\(\rho\)), cross-sectional pipe area…


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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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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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Basic Feedback Control Principles

Basic Feedback Control Principles

Feedback Control System Components Before we begin our discussion on process control, we must define a few key…


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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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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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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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Transmitter Damping Adjustments

Transmitter Damping Adjustments

The vast majority of modern process transmitters (both analog and digital) come equipped with a feature known…


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Electromagnetism Basics

Electromagnetism Basics

The fundamental principle of electromagnetism is that an electric current will create a magnetic field at…


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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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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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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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Limit, Selector, and Override Controls

Limit, Selector, and Override Controls

Another category of control strategies involves the use of signal relays or function blocks with the ability…


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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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Digital PID Algorithms

Digital PID Algorithms

Instrument technicians should not have to concern themselves over the programming details internal to digital…


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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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Resistance, Reactance and Impedance

Resistance, Reactance and Impedance

Electrical Resistance Resistance (\(R\)) is the dissipative opposition to an electric current, analogous to…


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Basic Feedback Control Principles

Basic Feedback Control Principles

Feedback Control System Components Before we begin our discussion on process control, we must define a few key…


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Pipe and Pipe Fittings

Pipe and Pipe Fittings

Pipe is a hollow structure designed to provide an enclosed pathway for fluids to flow, usually manufactured…


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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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Proximity Switches

Proximity Switches

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


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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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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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Fundamental Principles of Industrial Instrumentation

Fundamental Principles of Industrial Instrumentation

Shown here is a partial listing of principles applied in the subject matter of this chapter, given for the…


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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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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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Atomic Theory and Chemical Symbols

Atomic Theory and Chemical Symbols

The three “elementary” particles of matter comprising all atoms are electrons, protons, and…


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Temperature Sensor Accessories

Temperature Sensor Accessories

One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…


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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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Numerical Differentiation

Numerical Differentiation

As we have seen, the concept of differentiation is finding the rate-of-change of one variable compared to…


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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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Single-line Electrical Diagrams

Single-line Electrical Diagrams

Electrical power grids primarily consist of three-phase AC circuits. This means most power lines (transmission…


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Fluid Power Systems

Fluid Power Systems

Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…


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How Derivatives and Integrals Relate to One Another

How Derivatives and Integrals Relate to One Another

First, let us review some of the properties of differentials and derivatives, referencing the expression and…


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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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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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Level Gauges (Sightglasses)

Level Gauges (Sightglasses)

Level gauges are perhaps the simplest indicating instrument for liquid level in a vessel. They are often found…


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