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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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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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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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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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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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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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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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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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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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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 purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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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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A wise PLC programmer once told me that the first thing any aspiring programmer should learn about the PLC…
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A pressure switch is one detecting the presence of fluid pressure. Pressure switches often use diaphragms or…
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For better or worse, there are no fewer than three different forms of PID equations implemented in modern PID…
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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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In November of 2007 a new computer virus was submitted to a virus scanning service. The purpose of this new…
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A proximity switch is one detecting the proximity (closeness) of some object. By definition, these switches…
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Finally, we arrive at the loop diagram (sometimes called a loop sheet) for the compressor surge control system…
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Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…
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Volumes could be written about poor diagnostic technique. The following mistakes are not intended to comprise…
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As we have seen, the concept of integration is finding the accumulation of one variable multiplied by another…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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A different strategy for controlling the flow of fluid is to insert a rotary element into the flow path.…
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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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Sample sizes of chemical substances are often measured in moles. One mole of a substance is defined as a…
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The following animation shows a rotating phasor in three-dimensional form. The phasor rotates in a complex…
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A quantitative PID tuning procedure is a step-by-step approach leading directly to a set of numerical values…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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Most of these formulae appear in molecular chemical form rather than structural form. For example, ethanol…
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