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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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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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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The transformer is one of the most important components in all of AC circuitry. Principally used to…
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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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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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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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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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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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By definition, a source is a device delivering energy into a system, while a load is a device extracting…
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Electrical power grids primarily consist of three-phase AC circuits. This means most power lines (transmission…
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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 concepts of calibration (trimming) and ranging are often difficult for new students of instrumentation to…
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A quantitative PID tuning procedure is a step-by-step approach leading directly to a set of numerical values…
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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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The next level of detail is the Process and Instrument Diagram, or P&ID. Here, we see a “zooming…
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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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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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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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A temperature switch is one detecting the temperature of some substance. Temperature switches often use…
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Self-balancing mechanisms consisting solely of a baffle/nozzle detector coupled to a feedback bellows, while…
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One of the most common, and most useful, pressure measuring instruments in industry is the differential…
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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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In November of 2007 a new computer virus was submitted to a virus scanning service. The purpose of this new…
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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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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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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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A fundamental principle in instrumentation system troubleshooting is that every instrument has at least one…
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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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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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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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