Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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Light is known to interact with matter in very specific ways, which may be exploited as a means of measuring…
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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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Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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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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Solids tend to expand when heated. The amount that a solid sample will expand with increased temperature…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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The fundamental principle of electromagnetism is that an electric current will create a magnetic field at…
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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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In order for any PID controller to be practical, it must be able to do more than just implement the PID…
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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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Another category of control strategies involves the use of signal relays or function blocks with the ability…
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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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Linearity of Measurement Instruments The purpose of calibration is to ensure the input and output of an…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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A great many precision instruments use the principle of balance to measure some quantity. Perhaps the simplest…
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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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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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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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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An variable-area flowmeter is one where the fluid must pass through a restriction whose area increases with…
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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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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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Coy, John J. et. al. (December 2012) Sampled graphic illustrations from his NASA Reference Publication…
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Layer 1 of the OSI Reference Model is where we define the “physical” elements of a digital data…
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To understand just how different FOUNDATION Fieldbus is from other digital instrument systems, consider a…
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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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Much of our knowledge about atomic structure comes from experimental data relating the interaction between…
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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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Sometimes we encounter a diversity of instrument signal standards in one control system. Such is the case with…
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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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Like so many other industrial data networks, FOUNDATION Fieldbus is an “unswitched” or…
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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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The following photograph shows a large air blower in a wastewater treatment facility equipped with a…
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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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The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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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 electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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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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A positive displacement flowmeter is a cyclic mechanism built to pass a fixed volume of fluid through with…
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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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A special type flowmeter suited for powdered or granular solids is the weighfeeder. One of the most common…
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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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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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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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By definition, a source is a device delivering energy into a system, while a load is a device extracting…
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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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Finally, we arrive at the loop diagram (sometimes called a loop sheet) for the compressor surge control system…
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Up until this point, we have explored various types of instrumentation diagram, each one making reference to…
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Control valves are supposed to deliver reliable, repeatable control of process fluid flow rate over a wide…
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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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In order to provide an interface between the internal (digital) world of a computer and the external (analog)…
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Electrical Resistance Resistance (\(R\)) is the dissipative opposition to an electric current, analogous to…
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