A limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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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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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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 reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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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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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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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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Learning how to tune PID controllers is a skill born of much practice. Regardless of how thoroughly you may…
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Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose…
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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 important rule to obey when using pneumatic instruments is to maintain clean and dry…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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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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A unique form of differential pressure-based flow measurement deserves its own section in this flow…
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An interesting parallel to the “unity fraction” unit conversion technique is something referred to…
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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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“Radio” systems use electromagnetic fields to communicate information over long distances through…
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For better or worse, there are no fewer than three different forms of PID equations implemented in modern PID…
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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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Modern analog-to-digital converters are phenomenally accurate, dependable, repeatable, and surprisingly…
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Perhaps the simplest form of solid or liquid level measurement is with a float: a device that rides on the…
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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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Impedance in a series circuit is the orthogonal sum of resistance and reactance: \[Z = \sqrt{R^2 + (X_L -…
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(Will be addressed in future versions of this book)
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