The key to understanding how three-phase electric motors work is to have an accurate mental picture of the…
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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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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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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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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 simplest form of 4-20 mA current loop is the type used to represent the output of a process controller,…
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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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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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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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A limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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 reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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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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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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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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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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 order for any PID controller to be practical, it must be able to do more than just implement the PID…
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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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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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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 bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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A quantitative PID tuning procedure is a step-by-step approach leading directly to a set of numerical values…
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Learning is not merely a process of information transfer. It is first and foremost a transformation of…
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The majority of flowmeter technologies operate on the principle of interpreting fluid flow based on the…
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Flow, by definition, is the passage of material from one location to another over time. So far this chapter…
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Once while working as an instrument technician in an aluminum foundry, a mechanic asked me what it was that I…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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The advent of “smart” field instruments containing microprocessors has been a great advance for…
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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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Regardless of valve type, all stem-actuated control valves require some form of seal allowing motion of the…
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In this section I will show screenshots from a process loop simulation program illustrating the effectiveness…
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Like so many other industrial data networks, FOUNDATION Fieldbus is an “unswitched” or…
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Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…
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Capacitive level instruments measure electrical capacitance of a conductive rod inserted vertically into a…
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All substances are comprised of various elements in various combinations and proportions. Elements may thus be…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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Sensors used to measure vibration come in three basic types: displacement, velocity, and acceleration.…
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Perhaps the most important rule to obey when using pneumatic instruments is to maintain clean and dry…
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In November of 2007 a new computer virus was submitted to a virus scanning service. The purpose of this new…
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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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