The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…
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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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A limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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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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The simplest form of 4-20 mA current loop is the type used to represent the output of a process controller,…
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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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Lipták, Béla G. et al., Instrument Engineers’ Handbook – Process Measurement and Analysis Volume I,…
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Regardless of valve type, all stem-actuated control valves require some form of seal allowing motion of the…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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Most people reading this book have likely had the experience of adjusting water temperature using two hand…
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Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…
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Atom: the smallest unit of matter that may be isolated by chemical means. Particle: a part of an atom,…
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The following animation shows how a radio-energy pulse travels down and then up the waveguide of a guided-wave…
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Converting between disparate units of measurement is the bane of many science students. The problem is worse…
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A special type flowmeter suited for powdered or granular solids is the weighfeeder. One of the most common…
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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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Some problem-solving techniques are unique to quantitative problems, involving mathematical calculations. In…
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Most of these formulae appear in molecular chemical form rather than structural form. For example, ethanol…
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Another category of control strategies involves the use of signal relays or function blocks with the ability…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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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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At the next OSI Reference Model layer (layer 4) is a set of protocols specifying how reliable communication…
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One very convenient feature of waves is that their properties are universal. Waves of water in the ocean,…
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These fortifications focus on human behavior rather than system design or component selection. In some ways…
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