A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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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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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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Most of these formulae appear in molecular chemical form rather than structural form. For example, ethanol…
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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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The three “elementary” particles of matter comprising all atoms are electrons, protons, and…
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The final step in treating wastewater before releasing it into the natural environment is to kill any harmful…
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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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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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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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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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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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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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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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One very convenient feature of waves is that their properties are universal. Waves of water in the ocean,…
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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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The following animation shows a rotating phasor in three-dimensional form. The phasor rotates in a complex…
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The following photograph shows a large air blower in a wastewater treatment facility equipped with a…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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Temperature measurement devices may be classified into two broad types: contact and non-contact. Contact-type…
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Electrical power grids primarily consist of three-phase AC circuits. This means most power lines (transmission…
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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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Regardless of valve type, all stem-actuated control valves require some form of seal allowing motion of the…
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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 fundamental principle of electromagnetism is that an electric current will create a magnetic field at…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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The most popular form of signal transmission used in modern industrial instrumentation systems (as of this…
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Mechanical pressure-sensing elements include the bellows, the diaphragm, and the bourdon tube. Each of these…
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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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Filled-bulb systems exploit the principle of fluid expansion to measure temperature. If a fluid is enclosed in…
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