The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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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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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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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 key to understanding how three-phase electric motors work is to have an accurate mental picture of 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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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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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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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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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 limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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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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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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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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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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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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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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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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The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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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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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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One of the most common, and most useful, pressure measuring instruments in industry is the differential…
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The key to understanding how three-phase electric motors work is to have an accurate mental picture of the…
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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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An important legacy technology for all kinds of continuous measurement is the self-balancing system. A…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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As previously defined, calibration refers to the checking and adjustment of an instrument so that its output…
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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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Pipe is a hollow structure designed to provide an enclosed pathway for fluids to flow, usually manufactured…
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Perhaps the most confusing aspect of discrete sensors is the definition of a sensor’s normal status.…
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In a manually-controlled process, a human operator directly actuates some form of final control element…
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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…
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An interesting parallel to the “unity fraction” unit conversion technique is something referred to…
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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 major marathon race, where hundreds of runners gather in one place to compete. When the starting gun…
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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float directly sets…
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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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A unique form of technical diagram for describing the abstract functions comprising a control system (e.g. PID…
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A control strategy similar to ratio control is relation control. This is similar to ratio control in that a…
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