Control valves are supposed to deliver reliable, repeatable control of process fluid flow rate over a wide…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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A flow switch is one that detects the flow of some fluid through a pipe. Flow switches often use…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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To show a practical process example, let’s examine three diagrams for a compressor control system,…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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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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Any power grid large enough to meet the demand of an entire nation must have multiple generators drawing from…
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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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Filled-bulb systems exploit the principle of fluid expansion to measure temperature. If a fluid is enclosed in…
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Perhaps the most confusing aspect of discrete sensors is the definition of a sensor’s normal status.…
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Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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Temperature measurement devices may be classified into two broad types: contact and non-contact. Contact-type…
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The vast majority of modern process transmitters (both analog and digital) come equipped with a feature known…
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Like many other mathematical operations, the derivative and the integral perform inverse operations from each…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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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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By definition, a source is a device delivering energy into a system, while a load is a device extracting…
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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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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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When control valves operate between fully open and fully shut, they serve much the same purpose in process…
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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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An important design parameter of a control valve is the position it will “fail” to if it loses…
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When a high-energy photon strikes an atom, it may eject one of the lower-level electrons from its shell,…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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The vast majority of modern process transmitters (both analog and digital) come equipped with a feature known…
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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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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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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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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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Learning how to tune PID controllers is a skill born of much practice. Regardless of how thoroughly you may…
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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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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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The majority of flowmeter technologies operate on the principle of interpreting fluid flow based on the…
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Fieldbus devices require far more attention in their initial setup and commissioning than their analog…
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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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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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One of the marks of a successful problem-solver is a habit of applying general principles to every new problem…
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The following animation shows a rotating phasor in three-dimensional form. The phasor rotates in a complex…
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Suppose we wished to measure the consumption of propane over time for a large propane storage tank supplying a…
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In reliability engineering, it is important to be able to quantity the reliability (or conversely, the…
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“As to methods there may be a million and then some, but principles are few. The man who grasps…
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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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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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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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Labwork is an essential part of any science-based curriculum. Here, much improvement may be made over the…
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In order for any PID controller to be practical, it must be able to do more than just implement the PID…
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A variety of technologies exist to measure the quantity of stored material in a vessel. For liquid…
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A temperature switch is one detecting the temperature of some substance. Temperature switches often use…
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