AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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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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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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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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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 simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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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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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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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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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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A limit switch detects the physical motion of an object by direct contact with that object. An example of 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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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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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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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 unique form of technical diagram for describing the abstract functions comprising a control system (e.g. PID…
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Self-balancing mechanisms consisting solely of a baffle/nozzle detector coupled to a feedback bellows, while…
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Any physical location in an industrial facility harboring the potential of explosion due to the presence of…
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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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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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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 chemical reaction resulting in a net release of energy is called exothermic. Conversely, a chemical reaction…
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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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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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It is possible to convey electrical power and communicate analog information over the same two wires using 4…
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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A unique form of differential pressure-based flow measurement deserves its own section in this flow…
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Sample sizes of chemical substances are often measured in moles. One mole of a substance is defined as a…
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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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One of the great benefits of digital technology is the ability to communicate vast amounts of information over…
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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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float directly sets…
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Weight-based level instruments sense process level in a vessel by directly measuring the weight of the vessel.…
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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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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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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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Self-balancing mechanisms consisting solely of a baffle/nozzle detector coupled to a feedback bellows, while…
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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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DC electric current signals may also be used to communicate process measurement information from transmitters…
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At the root of successful system diagnosis is a rigorous adherence to scientific reasoning. There exists no…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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All substances are comprised of various elements in various combinations and proportions. Elements may thus be…
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A much simpler alternative to continuous vibration sensors (displacement or acceleration) and monitoring…
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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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A very simple device used to measure pressure is the manometer: a fluid-filled tube where an applied gas…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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A variety of problem-solving techniques have been presented for students over the years which are all helpful…
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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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Some analyzers measure the composition of a process stream by directly immersing the sensing element in that…
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