AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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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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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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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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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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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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In November of 2007 a new computer virus was submitted to a virus scanning service. The purpose of this new…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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The very purpose of physics is to quantitatively describe and explain the physical world in as few terms as…
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There are many process control applications in the industry where it is desirable to have multiple control…
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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 following collection of photographs chronicles the complete disassembly of a Fisher E-body globe valve…
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Light has long been used as a long-range signaling medium. While communication by light through open air is…
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At the next OSI Reference Model layer (layer 4) is a set of protocols specifying how reliable communication…
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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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When a high-energy photon strikes an atom, it may eject one of the lower-level electrons from its shell,…
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Solids tend to expand when heated. The amount that a solid sample will expand with increased temperature…
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An exciting development in industrial instrumentation is the WirelessHART radio communication standard,…
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Much of our knowledge about atomic structure comes from experimental data relating the interaction between…
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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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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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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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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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Stoichiometry is the accounting of atoms before and after a chemical reaction. It is an expression of the Law…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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A quantitative PID tuning procedure is a step-by-step approach leading directly to a set of numerical values…
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