As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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A proximity switch is one detecting the proximity (closeness) of some object. By definition, these switches…
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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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Imagine a major marathon race, where hundreds of runners gather in one place to compete. When the starting gun…
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There is much to be said for neatness of assembly in electrical signal wiring. Even though the electrons…
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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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An variable-area flowmeter is one where the fluid must pass through a restriction whose area increases with…
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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…
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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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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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Converting between disparate units of measurement is the bane of many science students. The problem is worse…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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Most pneumatic instruments use a simple but highly sensitive mechanism for converting mechanical motion into…
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The majority of flowmeter technologies operate on the principle of interpreting fluid flow based on the…
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The advent of “smart” field instruments containing microprocessors has been a great advance for…
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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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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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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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Linearity of Measurement Instruments The purpose of calibration is to ensure the input and output of an…
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One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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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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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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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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A completely different way of measuring liquid level in vessels is to bounce a traveling wave off the surface…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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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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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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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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Light is known to interact with matter in very specific ways, which may be exploited as a means of measuring…
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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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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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The efficient identification and correction of instrument calibration errors is an important function for…
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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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One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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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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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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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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Classical mechanics (often called Newtonian mechanics in honor of Isaac Newton) deal with forces and motions…
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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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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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To review, voltage is the measure of potential energy available to electric charges. Current is the uniform…
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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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Light is known to interact with matter in very specific ways, which may be exploited as a means of measuring…
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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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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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The dispersion of visible light into its constituent colors goes all the way back to the 17th century with…
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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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Perhaps the simplest form of solid or liquid level measurement is with a float: a device that rides on the…
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In a manually-controlled process, a human operator directly actuates some form of final control element…
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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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A hand switch is exactly what the name implies: an electrical switch actuated by a person’s hand motion.…
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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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An variable-area flowmeter is one where the fluid must pass through a restriction whose area increases with…
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(Will be addressed in future versions of this book)
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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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Filled-bulb systems exploit the principle of fluid expansion to measure temperature. If a fluid is enclosed in…
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A variety of problem-solving techniques have been presented for students over the years which are all helpful…
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