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 purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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One of the simplest classes of temperature sensor is one where temperature effects a change in electrical…
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While the term “probability” may evoke images of imprecision, probability is in fact an exact…
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To understand just how different FOUNDATION Fieldbus is from other digital instrument systems, consider a…
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The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic 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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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…
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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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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…
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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 important design parameter of a control valve is the position it will “fail” to if it loses…
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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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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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A machine in the broad sense of the word is any device designed to translate some form of energy into useful…
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Temperature measurement devices may be classified into two broad types: contact and non-contact. Contact-type…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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One of the most common, and most useful, pressure measuring instruments in industry is the differential…
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Volumes could be written about poor diagnostic technique. The following mistakes are not intended to comprise…
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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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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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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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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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In addition to Ohm’s Law, we have a set of rules describing how voltages, currents, and resistances…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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Most people reading this book have likely had the experience of adjusting water temperature using two hand…
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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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A temperature switch is one detecting the temperature of some substance. Temperature switches often use…
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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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DC electric current signals may also be used to communicate process measurement information from transmitters…
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Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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Solids tend to expand when heated. The amount that a solid sample will expand with increased temperature…
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A pressure switch is one that detects the presence of fluid pressure. Pressure switches often use diaphragms…
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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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As we have seen, the concept of integration is finding the accumulation of one variable multiplied by another…
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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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As previously defined, calibration refers to the checking and adjustment of an instrument so that its output…
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A very common method for directly controlling low flow rates of fluids is to use a device known as a metering…
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Diagnostic ability is arguably the most difficult skill to develop within a student, and also the most…
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When I began teaching full-time in 1998, most of what I thought I understood about good teaching was actually…
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Volumes could be written about poor diagnostic technique. The following mistakes are not intended to comprise…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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Using filter cells to eliminate wavelengths associated with interfering gases is called positive filtering in…
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In reliability engineering, it is important to be able to quantity the reliability (or conversely, the…
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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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In a manually-controlled process, a human operator directly actuates some form of final control element…
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A fundamental principle in instrumentation system troubleshooting is that every instrument has at least one…
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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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The dispersion of visible light into its constituent colors goes all the way back to the 17th century with…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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To show a practical process example, let’s examine three diagrams for a compressor control system,…
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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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A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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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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Lipták, Béla G. et al., Instrument Engineers’ Handbook – Process Measurement and Analysis Volume I,…
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