An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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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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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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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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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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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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 vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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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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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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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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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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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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 limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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Suppose we wished to measure the consumption of propane over time for a large propane storage tank supplying a…
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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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A fluid is any substance having the ability to flow: to freely change shape and move under the influence of a…
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Light has long been used as a long-range signaling medium. While communication by light through open air is…
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A very common form of on/off valve used for pneumatic and hydraulic systems alike is the solenoid valve. A…
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One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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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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When control valves operate between fully open and fully shut, they serve much the same purpose in process…
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An important design parameter of a control valve is the position it will “fail” to if it loses…
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Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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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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Like so many other industrial data networks, FOUNDATION Fieldbus is an “unswitched” or…
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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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Suppose we wished to measure the rate of propane gas flow through a hose to a torch: Flowmeters appropriate…
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A level switch is one detecting the level of liquid or solid (granules or powder) in a vessel. Level switches…
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Feedback obtained from industrial users of FF reveal a common pattern: Fieldbus is a powerful and reliable…
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