The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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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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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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An engineer named Bob Metcalfe conceived the idea of Ethernet in 1973, while working for the Xerox research…
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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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Regardless of valve type, all stem-actuated control valves require some form of seal allowing motion of the…
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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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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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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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There are many process control applications in the industry where it is desirable to have multiple control…
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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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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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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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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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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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A limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…
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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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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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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 advent of “smart” field instruments containing microprocessors has been a great advance for…
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Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose…
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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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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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Linearity of Measurement Instruments The purpose of calibration is to ensure the input and output of an…
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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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Calculus has a reputation for being difficult to learn, and with good reason. The traditional approach to…
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The following animation shows how a radio-energy pulse travels down and then up the waveguide of a guided-wave…
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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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Solids tend to expand when heated. The amount that a solid sample will expand with increased temperature…
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A hand switch is exactly what the name implies: an electrical switch actuated by a person’s hand motion.…
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Many traditional flowmeter technologies respond to the volumetric flow rate of the moving fluid.…
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There is much to be said for neatness of assembly in electrical signal wiring. Even though the electrons…
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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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Any physical location in an industrial facility harboring the potential of explosion due to the presence of…
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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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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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Perhaps the simplest form of solid or liquid level measurement is with a float: a device that rides on the…
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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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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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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 important legacy technology for all kinds of continuous measurement is the self-balancing system. A…
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Some of the simplest types of digital communication networks found in industry are defined by the EIA…
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Weight-based level instruments sense process level in a vessel by directly measuring the weight of the vessel.…
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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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A limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Sensors used to measure vibration come in three basic types: displacement, velocity, and acceleration.…
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In November of 2007 a new computer virus was submitted to a virus scanning service. The purpose of this new…
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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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Many traditional flowmeter technologies respond to the volumetric flow rate of the moving fluid.…
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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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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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Certain types of nuclear radiation easily penetrates the walls of industrial vessels, but is attenuated by…
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To understand just how different FOUNDATION Fieldbus is from other digital instrument systems, consider a…
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A whole class of problem-solving techniques focuses on altering the given problem into a simpler form that is…
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