A form of protection against faults on long-distance power lines is called distance relaying, so named because…
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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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Any physical location in an industrial facility harboring the potential of explosion due to the presence of…
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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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The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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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 ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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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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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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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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Using filter cells to eliminate wavelengths associated with interfering gases is called positive filtering in…
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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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All masses require force to accelerate (we can also think of this in terms of the mass generating a reaction…
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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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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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While the term “probability” may evoke images of imprecision, probability is in fact an exact…
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A machine in the broad sense of the word is any device designed to translate some form of energy into useful…
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As a general rule, high achievement only takes place in an atmosphere of high expectations. Sometimes these…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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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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A control strategy similar to ratio control is relation control. This is similar to ratio control in that a…
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A unique form of differential pressure-based flow measurement deserves its own section in this flow…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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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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The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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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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A hand switch is exactly what the name implies: an electrical switch actuated by a person’s hand motion.…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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“As to methods there may be a million and then some, but principles are few. The man who grasps…
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Mechanical pressure-sensing elements include the bellows, the diaphragm, and the bourdon tube. Each of these…
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An important performance parameter for transmitter instruments is something often referred to as turndown or…
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A different strategy for controlling the flow of fluid is to insert a rotary element into the flow path.…
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