So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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Perhaps the most confusing aspect of discrete sensors is the definition of a sensor’s normal status.…
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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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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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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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A wise PLC programmer once told me that the first thing any aspiring programmer should learn about the PLC…
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Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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It is possible to convey electrical power and communicate analog information over the same two wires using 4…
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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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An variable-area flowmeter is one where the fluid must pass through a restriction whose area increases with…
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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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Since we often use electricity to convey energy from one location to another, it is important to be able to…
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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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A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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Recall that an exothermic chemical reaction is one that releases a net sum of energy, as opposed to an…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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To understand just how different FOUNDATION Fieldbus is from other digital instrument systems, consider a…
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Binary patterns are not just able to represent numerical values. Given a standardized code, they may represent…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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Every flow-measuring instrument exploits a physical principle to measure the flow rate of fluid stream.…
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Imagine a major marathon race, where hundreds of runners gather in one place to compete. When the starting gun…
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By definition, a source is a device delivering energy into a system, while a load is a device extracting…
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Some analyzers measure the composition of a process stream by directly immersing the sensing element in that…
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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 root of successful system diagnosis is a rigorous adherence to scientific reasoning. There exists no…
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Recall that an exothermic chemical reaction is one that releases a net sum of energy, as opposed to an…
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Most of these formulae appear in molecular chemical form rather than structural form. For example, ethanol…
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Learning from reading printed text is a kind of problem-solving activity it is own right. The problem is how…
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An important design parameter of a control valve is the position it will “fail” to if it loses…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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As we have seen, the concept of differentiation is finding the rate-of-change of one variable compared to…
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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 most common language used to program PLCs is Ladder Diagram (LD), also known as…
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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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Certain types of nuclear radiation easily penetrates the walls of industrial vessels, but is attenuated by…
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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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One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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The vast majority of modern process transmitters (both analog and digital) come equipped with a feature known…
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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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A laser is a light source emitting waves of light that not only share the exact same frequency (color)…
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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 concepts of calibration (trimming) and ranging are often difficult for new students of instrumentation to…
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Modern analog-to-digital converters are phenomenally accurate, dependable, repeatable, and surprisingly…
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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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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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