Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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A very common form of on/off valve used for pneumatic and hydraulic systems alike is the solenoid valve. A…
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Much of our knowledge about atomic structure comes from experimental data relating the interaction between…
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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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Any power grid large enough to meet the demand of an entire nation must have multiple generators drawing from…
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A level switch is one detecting the level of liquid or solid (granules or powder) in a vessel. Level switches…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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A much simpler alternative to continuous vibration sensors (displacement or acceleration) and monitoring…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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There is much to be said for neatness of assembly in electrical signal wiring. Even though the electrons…
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Binary patterns are not just able to represent numerical values. Given a standardized code, they may represent…
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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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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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Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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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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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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Thermodynamics is the study of heat, temperature, and their related effects in physical systems. As a subject,…
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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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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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In a manually-controlled process, a human operator directly actuates some form of final control element…
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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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By definition, a source is a device delivering energy into a system, while a load is a device extracting…
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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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One of the simplest classes of temperature sensor is one where temperature effects a change in electrical…
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As we have seen, the concept of differentiation is finding the rate-of-change of one variable compared to…
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In some process applications, it is important that the control valve be able to completely stop fluid flow…
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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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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One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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In addition to Ohm’s Law, we have a set of rules describing how voltages, currents, and resistances…
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Any conductor possesses a characteristic called inductance: the ability to store energy in the form of a…
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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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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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A different strategy for controlling the flow of fluid is to insert a rotary element into the flow path.…
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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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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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In a manually-controlled process, a human operator directly actuates some form of final control element…
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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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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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This section shows some of the many instrument symbols found in different types of technical diagrams used to…
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The majority of flowmeter technologies operate on the principle of interpreting fluid flow based on the…
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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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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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One of the great benefits of digital technology is the ability to communicate vast amounts of information over…
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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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DC electric current signals may also be used to communicate process measurement information from transmitters…
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To understand just how different FOUNDATION Fieldbus is from other digital instrument systems, consider a…
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Pipe is a hollow structure designed to provide an enclosed pathway for fluids to flow, usually manufactured…
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Perhaps the simplest form of solid or liquid level measurement is with a float: a device that rides on the…
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A powerful mathematical concept useful for analyzing practically any physical system – electrical…
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To review, voltage is the measure of potential energy available to electric charges. Current is the uniform…
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