Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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(Will be addressed in future versions of this book)
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In a manually-controlled process, a human operator directly actuates some form of final control element…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Many liquid substances undergo a process whereby their constituent molecules split into positively and…
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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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Area refers to the size of two-dimensional surface. Volume refers to the size of a three-dimensional space. To…
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A chemical reaction resulting in a net release of energy is called exothermic. Conversely, a chemical reaction…
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Current is the name we give to the motion of electric charges from a point of high potential to a point of low…
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pH is the measurement of the hydrogen ion activity in a liquid solution. It is one of the most common forms of…
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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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Much has been written about the benefits of robust PID control. Increased productivity, decreased equipment…
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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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In contrast to quantitative tuning procedures where definite numerical values for P, I, and D controller…
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A level switch is one detecting the level of liquid or solid (granules or powder) in a vessel. Level switches…
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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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A great many precision instruments use the principle of balance to measure some quantity. Perhaps the simplest…
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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 Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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The efficient identification and correction of instrument calibration errors is an important function for…
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An on/off valve is the fluid equivalent of an electrical switch: a device that either allows unimpeded flow or…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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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Measuring the flow rate of liquid through an open channel is not unlike measuring the flow rate of a liquid…
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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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Most pneumatic instruments use a simple but highly sensitive mechanism for converting mechanical motion into…
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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 disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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(Will be addressed in future versions of this book)
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An important legacy technology for all kinds of continuous measurement is the self-balancing system. A…
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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 flow switch is one detecting the flow of some fluid through a pipe. Flow switches often use…
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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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Some analyzers measure the composition of a process stream by directly immersing the sensing element in that…
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A limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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Most people reading this book have likely had the experience of adjusting water temperature using two hand…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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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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A powerful mathematical concept useful for analyzing practically any physical system – electrical…
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