Sometimes we encounter a diversity of instrument signal standards in one control system. Such is the case with…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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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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By definition, a source is a device delivering energy into a system, while a load is a device extracting…
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One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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The transformer is one of the most important components in all of AC circuitry. Principally used to…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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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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Since we often use electricity to convey energy from one location to another, it is important to be able to…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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Electrical power grids primarily consist of three-phase AC circuits. This means most power lines (transmission…
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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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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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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…
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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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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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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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The concepts of calibration (trimming) and ranging are often difficult for new students of instrumentation to…
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Shown here is a partial listing of principles applied in the subject matter of this chapter, given for the…
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Once while working as an instrument technician in an aluminum foundry, a mechanic asked me what it was that I…
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Learning how to tune PID controllers is a skill born of much practice. Regardless of how thoroughly you may…
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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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At the root of successful system diagnosis is a rigorous adherence to scientific reasoning. There exists no…
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In this section I will show screenshots from a process loop simulation program illustrating the effectiveness…
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It is possible to convey electrical power and communicate analog information over the same two wires using 4…
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Measuring the flow rate of liquid through an open channel is not unlike measuring the flow rate of a liquid…
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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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Mechanical pressure-sensing elements include the bellows, the diaphragm, and the bourdon tube. Each of these…
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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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Most pneumatic instruments use a simple but highly sensitive mechanism for converting mechanical motion into…
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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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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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