Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets 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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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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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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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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 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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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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 order for any PID controller to be practical, it must be able to do more than just implement the PID…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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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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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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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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Tube, like pipe, is a hollow structure designed to provide an enclosed pathway for fluids to flow. In the case…
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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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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 whole class of problem-solving techniques focuses on altering the given problem into a simpler form that is…
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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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Some analyzers measure the composition of a process stream by directly immersing the sensing element in that…
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Certain types of nuclear radiation easily penetrates the walls of industrial vessels, but is attenuated by…
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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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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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An exciting development in industrial instrumentation is the WirelessHART radio communication standard,…
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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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Fluid pressure exerts force on any surface area it contacts, as described by the formula \(F = PA\). One…
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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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The following photograph shows a large air blower in a wastewater treatment facility equipped with a…
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A level switch is one detecting the level of liquid or solid (granules or powder) in a vessel. Level switches…
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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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Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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(Will be addressed in future versions of this book)
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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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An important design parameter of a control valve is the position it will “fail” to if it loses…
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