“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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There are multiple motives for compromising the security of an industrial control system, some of which…
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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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A design-based fortification is one rooted in technical details of system architecture and functionality. Some…
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Fieldbus devices require far more attention in their initial setup and commissioning than their analog…
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A 4 to 20 mA current signal represents some signal along a 0 to 100 percent scale. Usually, this scale is…
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These fortifications focus on human behavior rather than system design or component selection. In some ways…
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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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A unique form of technical diagram for describing the abstract functions comprising a control system (e.g. PID…
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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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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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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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Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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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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The advent of “smart” field instruments containing microprocessors has been a great advance for…
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An exciting development in industrial instrumentation is the WirelessHART radio communication standard,…
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Light has long been used as a long-range signaling medium. While communication by light through open air is…
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In this section I will show screenshots from a process loop simulation program illustrating the effectiveness…
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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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Any physical location in an industrial facility harboring the potential of explosion due to the presence of…
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(Will be addressed in future versions of this book)
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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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Impedance in a series circuit is the orthogonal sum of resistance and reactance: \[Z = \sqrt{R^2 + (X_L -…
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A variety of technologies exist to measure the quantity of stored material in a vessel. For liquid…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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Volumes could be written about poor diagnostic technique. The following mistakes are not intended to comprise…
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Visualizing the actions of P, I, and D tuning parameters using graphs is extremely useful in predicting the…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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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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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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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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Another category of control strategies involves the use of signal relays or function blocks with the ability…
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“As to methods there may be a million and then some, but principles are few. The man who grasps…
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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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Many years ago, when I was first learning about electricity, I happened to discover a length of coaxial…
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The following animation shows how a radio-energy pulse travels down and then up the waveguide of a guided-wave…
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One of the most common, and most useful, pressure measuring instruments in industry is the differential…
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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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A much simpler alternative to continuous vibration sensors (displacement or acceleration) and monitoring…
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A variety of technologies exist to measure the quantity of stored material in a vessel. For liquid…
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Earlier in this chapter you were shown a model of a nitrogen atom with a dense nucleus (comprised of protons…
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A fundamental limitation of proportional control has to do with its response to changes in setpoint and…
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A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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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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Much of our knowledge about atomic structure comes from experimental data relating the interaction between…
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Many liquid substances undergo a process whereby their constituent molecules split into positively and…
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All substances are comprised of various elements in various combinations and proportions. Elements may thus be…
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Converting between disparate units of measurement is the bane of many science students. The problem is worse…
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Every flow-measuring instrument exploits a physical principle to measure the flow rate of fluid stream.…
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Although analog electronic process controllers are considered a newer technology than pneumatic process…
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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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By definition, a source is a device delivering energy into a system, while a load is a device extracting…
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A vertical column of fluid generates a pressure at the bottom of the column owing to the action of gravity on…
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