DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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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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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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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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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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 addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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 simple control system drawn in block diagram form looks like this: Information from the measuring device…
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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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What is Calibration? To calibrate an instrument means to check and adjust (if necessary) its response so the…
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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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Level gauges are perhaps the simplest indicating instrument for liquid level in a vessel. They are often found…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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The concepts of calibration (trimming) and ranging are often difficult for new students of instrumentation to…
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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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A limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…
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A hand switch is exactly what the name implies: an electrical switch actuated by a person’s hand motion.…
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Learning how to tune PID controllers is a skill born of much practice. Regardless of how thoroughly you may…
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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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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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In contrast to quantitative tuning procedures where definite numerical values for P, I, and D controller…
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All masses require force to accelerate (we can also think of this in terms of the mass generating a reaction…
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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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Labwork is an essential part of any science-based curriculum. Here, much improvement may be made over the…
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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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Solids tend to expand when heated. The amount that a solid sample will expand with increased temperature…
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