Perhaps the most confusing aspect of discrete sensors is the definition of a sensor’s normal status.…
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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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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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A wise PLC programmer once told me that the first thing any aspiring programmer should learn about the PLC…
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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 pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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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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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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“Radio” systems use electromagnetic fields to communicate information over long distances through…
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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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One of the great benefits of digital technology is the ability to communicate vast amounts of information over…
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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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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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Volumes could be written about poor diagnostic technique. The following mistakes are not intended to comprise…
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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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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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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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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 term “grid” refers to the conductors and equipment interconnecting power sources to power…
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In order to provide an interface between the internal (digital) world of a computer and the external (analog)…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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Light has long been used as a long-range signaling medium. While communication by light through open air is…
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A proximity switch is one detecting the proximity (closeness) of some object. By definition, these switches…
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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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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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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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 on/off valve is the fluid equivalent of an electrical switch: a device that either allows unimpeded flow or…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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Like so many other industrial data networks, FOUNDATION Fieldbus is an “unswitched” or…
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In modern industry, the most popular form of field-level signal transmission for variable industrial…
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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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As previously defined, calibration refers to the checking and adjustment of an instrument so that its output…
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(Will be addressed in future versions of this book)
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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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While the term “probability” may evoke images of imprecision, probability is in fact an exact…
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Nearly every technical course teaches and tests students on definitions, basic concepts, and at least some…
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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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Modern analog-to-digital converters are phenomenally accurate, dependable, repeatable, and surprisingly…
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Many years ago, when I was first learning about electricity, I happened to discover a length of coaxial…
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A form of protection against faults on long-distance power lines is called distance relaying, so named because…
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