A machine in the broad sense of the word is any device designed to translate some form of energy into useful…
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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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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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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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Since we often use electricity to convey energy from one location to another, it is important to be able 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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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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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 transformer is one of the most important components in all of AC circuitry. Principally used to…
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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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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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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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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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Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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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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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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The simplest form of 4-20 mA current loop is the type used to represent the output of a process controller,…
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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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Coy, John J. et. al. (December 2012) Sampled graphic illustrations from his NASA Reference Publication…
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Linearity of Measurement Instruments The purpose of calibration is to ensure the input and output of an…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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Capacitive level instruments measure electrical capacitance of a conductive rod inserted vertically into a…
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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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The Law of Mass Conservation states that matter can neither be created nor destroyed. The Law of Energy…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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A limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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A very simple device used to measure pressure is the manometer: a fluid-filled tube where an applied gas…
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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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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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PID control can be a confusing concept to understand. Here, a brief summary of each term within PID (P. I, and…
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Many traditional flowmeter technologies respond to the volumetric flow rate of the moving fluid.…
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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…
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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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