Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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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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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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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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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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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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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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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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A fundamental limitation of proportional control has to do with its response to changes in setpoint and…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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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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As we have seen, feedforward control is a way to improve the stability of a feedback control system in the…
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Many years ago, when I was first learning about electricity, I happened to discover a length of coaxial…
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Area refers to the size of two-dimensional surface. Volume refers to the size of a three-dimensional space. To…
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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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Fieldbus devices require far more attention in their initial setup and commissioning than their analog…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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A limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…
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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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A special type flowmeter suited for powdered or granular solids is the weighfeeder. One of the most common…
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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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The Law of Continuity for fluids states that the product of mass density (\(\rho\)), cross-sectional pipe area…
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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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Some problem-solving techniques are unique to quantitative problems, involving mathematical calculations. In…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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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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Electrical Resistance Resistance (\(R\)) is the dissipative opposition to an electric current, analogous to…
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These fortifications focus on human behavior rather than system design or component selection. In some ways…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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When control valves operate between fully open and fully shut, they serve much the same purpose in process…
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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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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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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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The most popular form of signal transmission used in modern industrial instrumentation systems (as of this…
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Using filter cells to eliminate wavelengths associated with interfering gases is called positive filtering in…
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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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A very common method for directly controlling low flow rates of fluids is to use a device known as a metering…
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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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Abdelaziz, Ahmed (June 2014) Identified numerous typographical errors throughout the book, mostly repeated…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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A temperature switch is one detecting the temperature of some substance. Temperature switches often use…
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Regardless of valve type, all stem-actuated control valves require some form of seal allowing motion of the…
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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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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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Most of these formulae appear in molecular chemical form rather than structural form. For example, ethanol…
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Hydrogen ion activity in aqueous (water-solvent) solutions is a very important parameter for a wide variety of…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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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Suppose we wished to measure the rate of propane gas flow through a hose to a torch: Flowmeters appropriate…
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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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As we have seen, feedforward control is a way to improve the stability of a feedback control system in 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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