Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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 the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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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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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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The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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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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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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A chemical reaction resulting in a net release of energy is called exothermic. Conversely, a chemical reaction…
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Nearly every technical course teaches and tests students on definitions, basic concepts, and at least some…
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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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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Fluid pressure exerts force on any surface area it contacts, as described by the formula \(F = PA\). One…
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A special type flowmeter suited for powdered or granular solids is the weighfeeder. One of the most common…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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Most pneumatic instruments use a simple but highly sensitive mechanism for converting mechanical motion into…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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 limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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Binary patterns are not just able to represent numerical values. Given a standardized code, they may represent…
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The most popular form of signal transmission used in modern industrial instrumentation systems (as of this…
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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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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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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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The very purpose of physics is to quantitatively describe and explain the physical world in as few terms as…
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I remember first learning about the world-wide Internet, and wondering what it actually looked like. The first…
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One of the great benefits of digital technology is the ability to communicate vast amounts of information over…
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A chemical reaction resulting in a net release of energy is called exothermic. Conversely, a chemical reaction…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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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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Visualizing the actions of P, I, and D tuning parameters using graphs is extremely useful in predicting the…
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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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A powerful mathematical concept useful for analyzing practically any physical system – electrical…
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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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Calculus has a reputation for being difficult to learn, and with good reason. The traditional approach to…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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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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One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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Atom: the smallest unit of matter that may be isolated by chemical means. Particle: a part of an atom,…
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One very convenient feature of waves is that their properties are universal. Waves of water in the ocean,…
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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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In some process applications, it is important that the control valve be able to completely stop fluid flow…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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All masses require force to accelerate (we can also think of this in terms of the mass generating a reaction…
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This section does not describe a particular type of flowmeter, but rather a design that may be implemented for…
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