A wise PLC programmer once told me that the first thing any aspiring programmer should learn about the PLC…
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Light is known to interact with matter in very specific ways, which may be exploited as a means of measuring…
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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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A fundamental limitation of proportional control has to do with its response to changes in setpoint and…
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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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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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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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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float directly sets…
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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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One very convenient feature of waves is that their properties are universal. Waves of water in the ocean,…
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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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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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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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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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In a manually-controlled process, a human operator directly actuates some form of final control element…
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Learning from reading printed text is a kind of problem-solving activity it is own right. The problem is how…
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A fluid is any substance having the ability to flow: to freely change shape and move under the influence of a…
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Tube, like pipe, is a hollow structure designed to provide an enclosed pathway for fluids to flow. In the case…
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Temperature measurement devices may be classified into two broad types: contact and non-contact. Contact-type…
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A much simpler alternative to continuous vibration sensors (displacement or acceleration) and monitoring…
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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 most confusing aspect of discrete sensors is the definition of a sensor’s normal status.…
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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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Shown here is a partial listing of principles applied in the subject matter of this chapter, given for the…
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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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A special type flowmeter suited for powdered or granular solids is the weighfeeder. One of the most common…
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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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The key to understanding how three-phase electric motors work is to have an accurate mental picture of the…
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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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Sometimes we encounter a diversity of instrument signal standards in one control system. Such is the case with…
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(Will be addressed in future versions of this book)
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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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Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…
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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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It is often useful to express the amplitude of an alternating quantity such as voltage or current in terms…
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The most popular form of signal transmission used in modern industrial instrumentation systems (as of this…
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Some self-powered (4-wire) analog electronic transmitters are designed to behave as electrical loads rather…
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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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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 Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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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 sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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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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An variable-area flowmeter is one where the fluid must pass through a restriction whose area increases with…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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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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A very common form of on/off valve used for pneumatic and hydraulic systems alike is the solenoid valve. A…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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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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Like so many other industrial data networks, FOUNDATION Fieldbus is an “unswitched” or…
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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 dispersion of visible light into its constituent colors goes all the way back to the 17th century with…
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