AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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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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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 simplest form of 4-20 mA current loop is the type used to represent the output of a process controller,…
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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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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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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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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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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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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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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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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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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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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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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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing 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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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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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 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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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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A control strategy similar to ratio control is relation control. This is similar to ratio control in that a…
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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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An exciting development in industrial instrumentation is the WirelessHART radio communication standard,…
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Much has been written about the benefits of robust PID control. Increased productivity, decreased equipment…
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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 is much to be said for neatness of assembly in electrical signal wiring. Even though the electrons…
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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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Suppose we wished to measure the rate of propane gas flow through a hose to a torch: Flowmeters appropriate…
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Certain types of nuclear radiation easily penetrates the walls of industrial vessels, but is attenuated by…
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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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Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…
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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 great many precision instruments use the principle of balance to measure some quantity. Perhaps the simplest…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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A design-based fortification is one rooted in technical details of system architecture and functionality. Some…
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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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The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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In modern industry, the most popular form of field-level signal transmission for variable industrial…
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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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The final step in treating wastewater before releasing it into the natural environment is to kill any harmful…
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