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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There are many process control applications in the industry where it is desirable to have multiple control…
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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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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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When control valves operate between fully open and fully shut, they serve much the same purpose in process…
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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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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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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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Learning PLC programming is a very important skill. If your job involves programming, then you will likely…
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As we have seen, the concept of integration is finding the accumulation of one variable multiplied by another…
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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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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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The transformer is one of the most important components in all of AC circuitry. Principally used to…
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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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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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The efficient identification and correction of instrument calibration errors is an important function for…
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Suppose we wished to measure the consumption of propane over time for a large propane storage tank supplying a…
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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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Finally, we arrive at the loop diagram (sometimes called a loop sheet) for the compressor surge control system…
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Some analyzers measure the composition of a process stream by directly immersing the sensing element in that…
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An interesting parallel to the “unity fraction” unit conversion technique is something referred to…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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Shown here is a partial listing of principles applied in the subject matter of this chapter, given for the…
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The advent of “smart” field instruments containing microprocessors has been a great advance for…
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The key to understanding how three-phase electric motors work is to have an accurate mental picture of the…
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Creative Commons Attribution 4.0 International Public License By exercising the Licensed Rights (defined…
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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…
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An exciting development in industrial instrumentation is the WirelessHART radio communication standard,…
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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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An important design parameter of a control valve is the position it will “fail” to if it loses…
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A control strategy similar to ratio control is relation control. This is similar to ratio control in that a…
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Area refers to the size of two-dimensional surface. Volume refers to the size of a three-dimensional space. To…
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A unique form of differential pressure-based flow measurement deserves its own section in this flow…
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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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(Will be addressed in future versions of this book)
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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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What is Calibration? To calibrate an instrument means to check and adjust (if necessary) its response so the…
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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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By definition, a source is a device delivering energy into a system, while a load is a device extracting…
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Capacitive level instruments measure electrical capacitance of a conductive rod inserted vertically into a…
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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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One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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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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The Law of Mass Conservation states that matter can neither be created nor destroyed. The Law of Energy…
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Current is the name we give to the motion of electric charges from a point of high potential to a point of low…
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Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose…
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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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One of the marks of a successful problem-solver is a habit of applying general principles to every new problem…
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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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pH is the measurement of the hydrogen ion activity in a liquid solution. It is one of the most common forms of…
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(Will be addressed in future versions of this book)
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Imagine a major marathon race, where hundreds of runners gather in one place to compete. When the starting gun…
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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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Sometimes we encounter a diversity of instrument signal standards in one control system. Such is the case with…
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To show a practical process example, let’s examine three diagrams for a compressor control system,…
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