Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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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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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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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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All masses require force to accelerate (we can also think of this in terms of the mass generating a reaction…
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Modern analog-to-digital converters are phenomenally accurate, dependable, repeatable, and surprisingly…
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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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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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Any physical location in an industrial facility harboring the potential of explosion due to the presence of…
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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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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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Learning PLC programming is a very important skill. If your job involves programming, then you will likely…
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Labwork is an essential part of any science-based curriculum. Here, much improvement may be made over the…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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A temperature switch is one detecting the temperature of some substance. Temperature switches often use…
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Volumes could be written about poor diagnostic technique. The following mistakes are not intended to comprise…
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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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One of the most common, and most useful, pressure measuring instruments in industry is the differential…
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Sometimes we encounter a diversity of instrument signal standards in one control system. Such is the case with…
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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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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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Regardless of valve type, all stem-actuated control valves require some form of seal allowing motion of the…
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A chemical reaction resulting in a net release of energy is called exothermic. Conversely, a chemical reaction…
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Another category of control strategies involves the use of signal relays or function blocks with the ability…
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Fieldbus devices require far more attention in their initial setup and commissioning than their analog…
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All substances are comprised of various elements in various combinations and proportions. Elements may thus be…
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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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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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To show a practical process example, let’s examine three diagrams for a compressor control system,…
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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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A unique form of differential pressure-based flow measurement deserves its own section in this flow…
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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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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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