The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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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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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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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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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 simple control system drawn in block diagram form looks like this: Information from the measuring device…
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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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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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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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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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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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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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 purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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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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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…
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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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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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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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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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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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The vast majority of modern process transmitters (both analog and digital) come equipped with a feature known…
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“Radio” systems use electromagnetic fields to communicate information over long distances through…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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In some process applications, it is important that the control valve be able to completely stop fluid flow…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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Measuring the flow rate of liquid through an open channel is not unlike measuring the flow rate of a liquid…
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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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Weight-based level instruments sense process level in a vessel by directly measuring the weight of the vessel.…
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The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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The transformer is one of the most important components in all of AC circuitry. Principally used to…
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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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Any power grid large enough to meet the demand of an entire nation must have multiple generators drawing from…
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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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What is Calibration? To calibrate an instrument means to check and adjust (if necessary) its response so the…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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pH is the measurement of the hydrogen ion activity in a liquid solution. It is one of the most common forms of…
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Suppose we wished to measure the rate of propane gas flow through a hose to a torch: Flowmeters appropriate…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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