Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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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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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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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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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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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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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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There are multiple motives for compromising the security of an industrial control system, some of which…
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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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At the next OSI Reference Model layer (layer 4) is a set of protocols specifying how reliable communication…
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Once while working as an instrument technician in an aluminum foundry, a mechanic asked me what it was that I…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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It is often useful to express the amplitude of an alternating quantity such as voltage or current in terms…
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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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One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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Volumes could be written about poor diagnostic technique. The following mistakes are not intended to comprise…
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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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The three “elementary” particles of matter comprising all atoms are electrons, protons, and…
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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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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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Thermodynamics is the study of heat, temperature, and their related effects in physical systems. As a subject,…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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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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DC electric current signals may also be used to communicate process measurement information from transmitters…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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