As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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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 simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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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 purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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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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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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 simple control system drawn in block diagram form looks like this: Information from the measuring device…
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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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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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A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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Suppose we wished to measure the rate of propane gas flow through a hose to a torch: Flowmeters appropriate…
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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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Filled-bulb systems exploit the principle of fluid expansion to measure temperature. If a fluid is enclosed in…
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“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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Learning how to tune PID controllers is a skill born of much practice. Regardless of how thoroughly you may…
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Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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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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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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One of the most common, and most useful, pressure measuring instruments in industry is the differential…
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When a high-energy photon strikes an atom, it may eject one of the lower-level electrons from its shell,…
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Perhaps the simplest form of solid or liquid level measurement is with a float: a device that rides on the…
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In this section I will show screenshots from a process loop simulation program illustrating the effectiveness…
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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 fundamental limitation of proportional control has to do with its response to changes in setpoint and…
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The final element of PID control is the “D” term, which stands for derivative. This is a calculus…
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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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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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Fluid pressure exerts force on any surface area it contacts, as described by the formula \(F = PA\). One…
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Stoichiometry is the accounting of atoms before and after a chemical reaction. It is an expression of the Law…
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A very simple device used to measure pressure is the manometer: a fluid-filled tube where an applied gas…
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Most of these formulae appear in molecular chemical form rather than structural form. For example, ethanol…
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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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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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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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Perhaps the most important rule to obey when using pneumatic instruments is to maintain clean and dry…
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Few areas of mathematics are as powerfully useful in describing and analyzing the physical world as calculus:…
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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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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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The next level of detail is the Process and Instrument Diagram, or P&ID. Here, we see a “zooming…
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In contrast to quantitative tuning procedures where definite numerical values for P, I, and D controller…
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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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An important legacy technology for all kinds of continuous measurement is the self-balancing system. A…
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A flow switch is one detecting the flow of some fluid through a pipe. Flow switches often use…
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To understand just how different FOUNDATION Fieldbus is from other digital instrument systems, consider a…
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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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Valves can experience a number of problems, most of them either preventable or repairable. These problems can…
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