Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker 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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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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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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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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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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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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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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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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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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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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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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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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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 simple control system drawn in block diagram form looks like this: Information from the measuring device…
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In some process applications, it is important that the control valve be able to completely stop fluid flow…
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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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Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose…
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Modern analog-to-digital converters are phenomenally accurate, dependable, repeatable, and surprisingly…
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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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When control valves operate between fully open and fully shut, they serve much the same purpose in process…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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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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Another category of control strategies involves the use of signal relays or function blocks with the ability…
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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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Lipták, Béla G. et al., Instrument Engineers’ Handbook – Process Measurement and Analysis Volume I,…
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A proximity switch is one detecting the proximity (closeness) of some object. By definition, these switches…
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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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Atom: the smallest unit of matter that may be isolated by chemical means. Particle: a part of an atom,…
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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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A fundamental principle in instrumentation system troubleshooting is that every instrument has at least one…
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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…
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