There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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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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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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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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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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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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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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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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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust 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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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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A damper (otherwise known as a louvre) is a multi-element flow control device generally used to throttle large…
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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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Tube, like pipe, is a hollow structure designed to provide an enclosed pathway for fluids to flow. In the case…
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Some of the simplest types of digital communication networks found in industry are defined by the EIA…
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Thermodynamics is the study of heat, temperature, and their related effects in physical systems. As a subject,…
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Many liquid substances undergo a process whereby their constituent molecules split into positively and…
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A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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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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This section shows some of the many instrument symbols found in different types of technical diagrams used to…
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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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For better or worse, there are no fewer than three different forms of PID equations implemented in modern PID…
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An exciting development in industrial instrumentation is the WirelessHART radio communication standard,…
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(Will be addressed in future versions of this book)
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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One of the most common, and most useful, pressure measuring instruments in industry is the differential…
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The efficient identification and correction of instrument calibration errors is an important function for…
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A limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…
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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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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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