A form of protection against faults on long-distance power lines is called distance relaying, so named because…
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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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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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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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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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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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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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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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As we have seen, feedforward control is a way to improve the stability of a feedback control system in the…
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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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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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When a high-energy photon strikes an atom, it may eject one of the lower-level electrons from its shell,…
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Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…
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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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Perhaps the most confusing aspect of discrete sensors is the definition of a sensor’s normal status.…
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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 this section I will show screenshots from a process loop simulation program illustrating the effectiveness…
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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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Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose…
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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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Measuring the flow rate of liquid through an open channel is not unlike measuring the flow rate of a liquid…
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A form of protection against faults on long-distance power lines is called distance relaying, so named because…
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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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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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Once while working as an instrument technician in an aluminum foundry, a mechanic asked me what it was that I…
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Level gauges are perhaps the simplest indicating instrument for liquid level in a vessel. They are often found…
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All substances are comprised of various elements in various combinations and proportions. Elements may thus be…
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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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First, let us review some of the properties of differentials and derivatives, referencing the expression and…
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All masses require force to accelerate (we can also think of this in terms of the mass generating a reaction…
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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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Learning is not merely a process of information transfer. It is first and foremost a transformation of…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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A temperature switch is one detecting the temperature of some substance. Temperature switches often use…
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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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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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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 liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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The following animation shows the calculus concepts of differentiation and integration (with respect to time)…
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The efficient identification and correction of instrument calibration errors is an important function for…
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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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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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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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Capacitive level instruments measure electrical capacitance of a conductive rod inserted vertically into a…
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