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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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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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A limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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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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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as 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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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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This section does not describe a particular type of flowmeter, but rather a design that may be implemented for…
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One of the marks of a successful problem-solver is a habit of applying general principles to every new problem…
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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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Perhaps the most confusing aspect of discrete sensors is the definition of a sensor’s normal status.…
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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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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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Linearity of Measurement Instruments The purpose of calibration is to ensure the input and output of an…
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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 unique form of differential pressure-based flow measurement deserves its own section in this flow…
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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 proximity switch is one detecting the proximity (closeness) of some object. By definition, these switches…
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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 multiple motives for compromising the security of an industrial control system, some of which…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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(Will be addressed in future versions of this book)
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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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Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…
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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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