Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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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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The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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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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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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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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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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A limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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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When control valves operate between fully open and fully shut, they serve much the same purpose in process…
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Capacitive level instruments measure electrical capacitance of a conductive rod inserted vertically into a…
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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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Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…
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When I began teaching full-time in 1998, most of what I thought I understood about good teaching was actually…
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Solids tend to expand when heated. The amount that a solid sample will expand with increased temperature…
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A limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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Any physical location in an industrial facility harboring the potential of explosion due to the presence of…
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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 fundamental limitation of proportional control has to do with its response to changes in setpoint and…
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The three “elementary” particles of matter comprising all atoms are electrons, protons, and…
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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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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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The vast majority of modern process transmitters (both analog and digital) come equipped with a feature known…
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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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A damper (otherwise known as a louvre) is a multi-element flow control device generally used to throttle large…
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There are many process control applications in the industry where it is desirable to have multiple control…
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A form of protection against faults on long-distance power lines is called distance relaying, so named because…
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An important legacy technology for all kinds of continuous measurement is the self-balancing system. A…
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A damper (otherwise known as a louvre) is a multi-element flow control device generally used to throttle large…
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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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Shown here is a partial listing of principles applied in the subject matter of this chapter, given for the…
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A variety of technologies exist to measure the quantity of stored material in a vessel. For liquid…
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When a high-energy photon strikes an atom, it may eject one of the lower-level electrons from its shell,…
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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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Control valves are supposed to deliver reliable, repeatable control of process fluid flow rate over a wide…
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Self-balancing mechanisms consisting solely of a baffle/nozzle detector coupled to a feedback bellows, while…
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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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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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Coy, John J. et. al. (December 2012) Sampled graphic illustrations from his NASA Reference Publication…
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Classical mechanics (often called Newtonian mechanics in honor of Isaac Newton) deal with forces and motions…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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When I began teaching full-time in 1998, most of what I thought I understood about good teaching was actually…
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Like so many other industrial data networks, FOUNDATION Fieldbus is an “unswitched” or…
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Some problem-solving techniques are unique to quantitative problems, involving mathematical calculations. In…
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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Sample sizes of chemical substances are often measured in moles. One mole of a substance is defined as a…
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Take for instance the problem of measuring fluid flow through a pipe. To the layperson, this may seem to be a…
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