Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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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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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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A completely different way of measuring liquid level in vessels is to bounce a traveling wave off the surface…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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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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Diagnostic ability is arguably the most difficult skill to develop within a student, and also the most…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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Data-processing modules within FF systems are known as function blocks. Sometimes these blocks serve merely to…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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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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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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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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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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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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Light has long been used as a long-range signaling medium. While communication by light through open air is…
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Volumes could be written about poor diagnostic technique. The following mistakes are not intended to comprise…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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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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A proximity switch is one detecting the proximity (closeness) of some object. By definition, these switches…
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One of the most common, and most useful, pressure measuring instruments in industry is the differential…
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Impedance in a series circuit is the orthogonal sum of resistance and reactance: \[Z = \sqrt{R^2 + (X_L -…
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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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The key to understanding how three-phase electric motors work is to have an accurate mental picture of the…
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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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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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To show a practical process example, let’s examine three diagrams for a compressor control system,…
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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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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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Sample sizes of chemical substances are often measured in moles. One mole of a substance is defined as a…
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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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Visualizing the actions of P, I, and D tuning parameters using graphs is extremely useful in predicting the…
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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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There is much to be said for neatness of assembly in electrical signal wiring. Even though the electrons…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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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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Measuring the flow rate of liquid through an open channel is not unlike measuring the flow rate of a liquid…
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The final element of PID control is the “D” term, which stands for derivative. This is a calculus…
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Fluid pressure exerts force on any surface area it contacts, as described by the formula \(F = PA\). One…
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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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Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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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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Impedance in a series circuit is the orthogonal sum of resistance and reactance: \[Z = \sqrt{R^2 + (X_L -…
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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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A fundamental limitation of proportional control has to do with its response to changes in setpoint and…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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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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There are many process control applications in the industry where it is desirable to have multiple control…
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Flow, by definition, is the passage of material from one location to another over time. So far this chapter…
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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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A number of different sensors used in instrumentation generate DC voltage signals proportional to the 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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Learning PLC programming is a very important skill. If your job involves programming, then you will likely…
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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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