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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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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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 following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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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 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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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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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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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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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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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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A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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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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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…
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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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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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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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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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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
Textbook
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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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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An important performance parameter for transmitter instruments is something often referred to as turndown or…
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In reliability engineering, it is important to be able to quantity the reliability (or conversely, the…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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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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Perhaps the most important rule to obey when using pneumatic instruments is to maintain clean and dry…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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An variable-area flowmeter is one where the fluid must pass through a restriction whose area increases with…
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Certain types of nuclear radiation easily penetrates the walls of industrial vessels, but is attenuated by…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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Perhaps the simplest form of solid or liquid level measurement is with a float: a device that rides on the…
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Finally, we arrive at the loop diagram (sometimes called a loop sheet) for the compressor surge control system…
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In contrast to quantitative tuning procedures where definite numerical values for P, I, and D controller…
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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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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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As we have seen, the concept of differentiation is finding the rate-of-change of one variable compared to…
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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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It is possible to convey electrical power and communicate analog information over the same two wires using 4…
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