Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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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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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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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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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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Modern analog-to-digital converters are phenomenally accurate, dependable, repeatable, and surprisingly…
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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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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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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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One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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Classical mechanics (often called Newtonian mechanics in honor of Isaac Newton) deal with forces and motions…
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Using filter cells to eliminate wavelengths associated with interfering gases is called positive filtering in…
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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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A form of protection against faults on long-distance power lines is called distance relaying, so named because…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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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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Learning is not merely a process of information transfer. It is first and foremost a transformation of…
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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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Weight-based level instruments sense process level in a vessel by directly measuring the weight of the vessel.…
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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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Impedance in a series circuit is the orthogonal sum of resistance and reactance: \[Z = \sqrt{R^2 + (X_L -…
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The next level of detail is the Process and Instrument Diagram, or P&ID. Here, we see a “zooming…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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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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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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It is often useful to express the amplitude of an alternating quantity such as voltage or current in terms…
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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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Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…
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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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Labwork is an essential part of any science-based curriculum. Here, much improvement may be made over the…
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An interesting parallel to the “unity fraction” unit conversion technique is something referred to…
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One very convenient feature of waves is that their properties are universal. Waves of water in the ocean,…
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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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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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Control valves are supposed to deliver reliable, repeatable control of process fluid flow rate over a wide…
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