The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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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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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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The key to understanding how three-phase electric motors work is to have an accurate mental picture of the…
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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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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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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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 simple control system drawn in block diagram form looks like this: Information from the measuring device…
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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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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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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A limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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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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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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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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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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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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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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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Sample sizes of chemical substances are often measured in moles. One mole of a substance is defined as a…
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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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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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Since we often use electricity to convey energy from one location to another, it is important to be able to…
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A pressure switch is one that detects the presence of fluid pressure. Pressure switches often use diaphragms…
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The next level of detail is the Process and Instrument Diagram, or P&ID. Here, we see a “zooming…
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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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While the term “probability” may evoke images of imprecision, probability is in fact an exact…
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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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Many years ago, when I was first learning about electricity, I happened to discover a length of coaxial…
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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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As we have seen, the concept of integration is finding the accumulation of one variable multiplied by another…
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A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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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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Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…
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Self-balancing mechanisms consisting solely of a baffle/nozzle detector coupled to a feedback bellows, while…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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An on/off valve is the fluid equivalent of an electrical switch: a device that either allows unimpeded flow or…
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Data-processing modules within FF systems are known as function blocks. Sometimes these blocks serve merely to…
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