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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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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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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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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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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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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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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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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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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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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A unique form of differential pressure-based flow measurement deserves its own section in this flow…
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Many years ago, when I was first learning about electricity, I happened to discover a length of coaxial…
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Steam boilers are very common in industry, principally because steam power is so useful. Common uses for steam…
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While the term “probability” may evoke images of imprecision, probability is in fact an exact…
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Imagine a major marathon race, where hundreds of runners gather in one place to compete. When the starting gun…
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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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Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…
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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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A proximity switch is one detecting the proximity (closeness) of some object. By definition, these switches…
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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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Learning from reading printed text is a kind of problem-solving activity it is own right. The problem is how…
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An on/off valve is the fluid equivalent of an electrical switch: a device that either allows unimpeded flow or…
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pH is the measurement of the hydrogen ion activity in a liquid solution. It is one of the most common forms of…
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A flow switch is one that detects the flow of some fluid through a pipe. Flow switches often use…
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Fieldbus devices require far more attention in their initial setup and commissioning than their analog…
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(Will be addressed in future versions of this book)
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