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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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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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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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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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 electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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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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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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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 motors generate torque by a reaction between two magnetic fields: one field established by…
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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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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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A unique form of technical diagram for describing the abstract functions comprising a control system (e.g. PID…
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Some of the simplest types of digital communication networks found in industry are defined by the EIA…
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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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An important performance parameter for transmitter instruments is something often referred to as turndown or…
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In addition to Ohm’s Law, we have a set of rules describing how voltages, currents, and resistances…
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Data-processing modules within FF systems are known as function blocks. Sometimes these blocks serve merely to…
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Temperature measurement devices may be classified into two broad types: contact and non-contact. Contact-type…
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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float directly sets…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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As we have seen, feedforward control is a way to improve the stability of a feedback control system in the…
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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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Diagnostic ability is arguably the most difficult skill to develop within a student, and also the most…
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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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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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To review, voltage is the measure of potential energy available to electric charges. Current is the uniform…
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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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Take for instance the problem of measuring fluid flow through a pipe. To the layperson, this may seem to be a…
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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