“Radio” systems use electromagnetic fields to communicate information over long distances through…
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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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Electrical power grids primarily consist of three-phase AC circuits. This means most power lines (transmission…
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To show a practical process example, let’s examine three diagrams for a compressor control system,…
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A pressure switch is one detecting the presence of fluid pressure. Pressure switches often use diaphragms or…
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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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Many liquid substances undergo a process whereby their constituent molecules split into positively and…
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“As to methods there may be a million and then some, but principles are few. The man who grasps…
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“Radio” systems use electromagnetic fields to communicate information over long distances through…
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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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Visualizing the actions of P, I, and D tuning parameters using graphs is extremely useful in predicting the…
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This section shows some of the many instrument symbols found in different types of technical diagrams used 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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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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Fluid pressure exerts force on any surface area it contacts, as described by the formula \(F = PA\). One…
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Modern analog-to-digital converters are phenomenally accurate, dependable, repeatable, and surprisingly…
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The Law of Mass Conservation states that matter can neither be created nor destroyed. The Law of Energy…
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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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As we have seen, feedforward control is a way to improve the stability of a feedback control system in the…
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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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The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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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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A unique form of differential pressure-based flow measurement deserves its own section in this 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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The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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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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This section does not describe a particular type of flowmeter, but rather a design that may be implemented for…
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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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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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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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Stoichiometry is the accounting of atoms before and after a chemical reaction. It is an expression of the Law…
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The Law of Continuity for fluids states that the product of mass density (\(\rho\)), cross-sectional pipe area…
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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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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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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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A special type flowmeter suited for powdered or granular solids is the weighfeeder. One of the most common…
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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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An interesting parallel to the “unity fraction” unit conversion technique is something referred to…
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Hydrogen ion activity in aqueous (water-solvent) solutions is a very important parameter for a wide variety of…
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