“Polyphase” means “many phases,” describing a form of AC electrical system where…
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In reliability engineering, it is important to be able to quantity the reliability (or conversely, the…
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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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As we have seen, feedforward control is a way to improve the stability of a feedback control system in the…
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Fieldbus devices require far more attention in their initial setup and commissioning than their analog…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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Tube, like pipe, is a hollow structure designed to provide an enclosed pathway for fluids to flow. In the case…
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A proximity switch is one detecting the proximity (closeness) of some object. By definition, these switches…
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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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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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An important legacy technology for all kinds of continuous measurement is the self-balancing system. A…
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At the next OSI Reference Model layer (layer 4) is a set of protocols specifying how reliable communication…
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A fluid is any substance having the ability to flow: to freely change shape and move under the influence of a…
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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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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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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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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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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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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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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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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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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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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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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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An engineer named Bob Metcalfe conceived the idea of Ethernet in 1973, while working for the Xerox research…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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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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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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One very convenient feature of waves is that their properties are universal. Waves of water in the ocean,…
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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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Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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A vertical column of fluid generates a pressure at the bottom of the column owing to the action of gravity on…
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The fundamental principle of electromagnetism is that an electric current will create a magnetic field at…
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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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Learning PLC programming is a very important skill. If your job involves programming, then you will likely…
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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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Classical mechanics (often called Newtonian mechanics in honor of Isaac Newton) deal with forces and motions…
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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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A control strategy similar to ratio control is relation control. This is similar to ratio control in that a…
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It is often useful to express the amplitude of an alternating quantity such as voltage or current in terms…
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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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The next level of detail is the Process and Instrument Diagram, or P&ID. Here, we see a “zooming…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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What is Calibration? To calibrate an instrument means to check and adjust (if necessary) its response so the…
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Sensors used to measure vibration come in three basic types: displacement, velocity, and acceleration.…
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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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A unique form of technical diagram for describing the abstract functions comprising a control system (e.g. PID…
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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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Converting between disparate units of measurement is the bane of many science students. The problem is worse…
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