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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The efficient identification and correction of instrument calibration errors is an important function for…
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The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…
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One of the simplest classes of temperature sensor is one where temperature effects a change in electrical…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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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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First, let us review some of the properties of differentials and derivatives, referencing the expression and…
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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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Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…
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As previously defined, calibration refers to the checking and adjustment of an instrument so that its output…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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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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Perhaps the most important rule to obey when using pneumatic instruments is to maintain clean and dry…
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Every flow-measuring instrument exploits a physical principle to measure the flow rate of fluid stream.…
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Much of our knowledge about atomic structure comes from experimental data relating the interaction between…
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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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The fundamental principle of electromagnetism is that an electric current will create a magnetic field at…
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Thermodynamics is the study of heat, temperature, and their related effects in physical systems. As a subject,…
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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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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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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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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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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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Current is the name we give to the motion of electric charges from a point of high potential to a point of low…
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Any conductor possesses a characteristic called inductance: the ability to store energy in the form of a…
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A very simple device used to measure pressure is the manometer: a fluid-filled tube where an applied gas…
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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 extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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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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One of the simplest classes of temperature sensor is one where temperature effects a change in electrical…
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A limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…
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A very simple device used to measure pressure is the manometer: a fluid-filled tube where an applied gas…
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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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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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In reliability engineering, it is important to be able to quantity the reliability (or conversely, the…
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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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Classical mechanics (often called Newtonian mechanics in honor of Isaac Newton) deal with forces and motions…
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When control valves operate between fully open and fully shut, they serve much the same purpose in process…
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Atom: the smallest unit of matter that may be isolated by chemical means. Particle: a part of an atom,…
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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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While the term “probability” may evoke images of imprecision, probability is in fact an exact…
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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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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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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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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 three “elementary” particles of matter comprising all atoms are electrons, protons, and…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…
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Steam boilers are very common in industry, principally because steam power is so useful. Common uses for steam…
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Visualizing the actions of P, I, and D tuning parameters using graphs is extremely useful in predicting the…
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