In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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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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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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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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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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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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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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 motors generate torque by a reaction between two magnetic fields: one field established by…
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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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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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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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 important rule of controller tuning is to know the process before attempting to adjust the…
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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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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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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 purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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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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A very simple device used to measure pressure is the manometer: a fluid-filled tube where an applied gas…
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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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A temperature switch is one detecting the temperature of some substance. Temperature switches often use…
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Learning from reading printed text is a kind of problem-solving activity it is own right. The problem is how…
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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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It is often useful to express the amplitude of an alternating quantity such as voltage or current in terms…
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An important design parameter of a control valve is the position it will “fail” to if it loses…
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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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A damper (otherwise known as a louvre) is a multi-element flow control device generally used to throttle large…
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Hydrogen ion activity in aqueous (water-solvent) solutions is a very important parameter for a wide variety of…
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Flow, by definition, is the passage of material from one location to another over time. So far this chapter…
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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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This section does not describe a particular type of flowmeter, but rather a design that may be implemented for…
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(Will be addressed in future versions of this book)
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Pipe is a hollow structure designed to provide an enclosed pathway for fluids to flow, usually manufactured…
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Feedback obtained from industrial users of FF reveal a common pattern: Fieldbus is a powerful and reliable…
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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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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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