Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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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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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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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The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing 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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express 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 technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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In November of 2007 a new computer virus was submitted to a virus scanning service. The purpose of this new…
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The efficient identification and correction of instrument calibration errors is an important function for…
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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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Some of the simplest types of digital communication networks found in industry are defined by the EIA…
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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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(Will be addressed in future versions of this book)
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There are multiple motives for compromising the security of an industrial control system, some of which…
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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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In reliability engineering, it is important to be able to quantity the reliability (or conversely, the…
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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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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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“Radio” systems use electromagnetic fields to communicate information over long distances through…
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Much of our knowledge about atomic structure comes from experimental data relating the interaction between…
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An important performance parameter for transmitter instruments is something often referred to as turndown or…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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Self-balancing mechanisms consisting solely of a baffle/nozzle detector coupled to a feedback bellows, while…
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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose…
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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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A design-based fortification is one rooted in technical details of system architecture and functionality. Some…
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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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The advent of “smart” field instruments containing microprocessors has been a great advance for…
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Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…
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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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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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“Radio” systems use electromagnetic fields to communicate information over long distances through…
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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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When control valves operate between fully open and fully shut, they serve much the same purpose in process…
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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 machine in the broad sense of the word is any device designed to translate some form of energy into useful…
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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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Self-balancing mechanisms consisting solely of a baffle/nozzle detector coupled to a feedback bellows, while…
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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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A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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A damper (otherwise known as a louvre) is a multi-element flow control device generally used to throttle large…
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The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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The most popular form of signal transmission used in modern industrial instrumentation systems (as of this…
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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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