When control valves operate between fully open and fully shut, they serve much the same purpose in process…
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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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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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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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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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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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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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A powerful mathematical concept useful for analyzing practically any physical system – electrical…
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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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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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A whole class of problem-solving techniques focuses on altering the given problem into a simpler form that is…
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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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Learning is not merely a process of information transfer. It is first and foremost a transformation of…
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Like so many other industrial data networks, FOUNDATION Fieldbus is an “unswitched” or…
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In a manually-controlled process, a human operator directly actuates some form of final control element…
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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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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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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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A pressure switch is one that detects the presence of fluid pressure. Pressure switches often use diaphragms…
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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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float directly sets…
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Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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As previously defined, calibration refers to the checking and adjustment of an instrument so that its output…
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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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Electrical Resistance Resistance (\(R\)) is the dissipative opposition to an electric current, analogous to…
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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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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 bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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In our first signal characterization example, we tackle the problem of measuring fluid flow through a pipe. To…
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As we have seen, feedforward control is a way to improve the stability of a feedback control system in the…
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Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing 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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Imagine a major marathon race, where hundreds of runners gather in one place to compete. When the starting gun…
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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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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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An important legacy technology for all kinds of continuous measurement is the self-balancing system. A…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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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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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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The very purpose of physics is to quantitatively describe and explain the physical world in as few terms as…
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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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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…
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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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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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All masses require force to accelerate (we can also think of this in terms of the mass generating a reaction…
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Calculus has a reputation for being difficult to learn, and with good reason. The traditional approach to…
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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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A fundamental principle in instrumentation system troubleshooting is that every instrument has at least one…
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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 three “elementary” particles of matter comprising all atoms are electrons, protons, and…
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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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