A limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…
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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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Take for instance the problem of measuring fluid flow through a pipe. To the layperson, this may seem to be a…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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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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An important design parameter of a control valve is the position it will “fail” to if it loses…
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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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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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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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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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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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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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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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Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float directly sets…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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There are many process control applications in the industry where it is desirable to have multiple control…
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Diagnostic ability is arguably the most difficult skill to develop within a student, and also the most…
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A fundamental limitation of proportional control has to do with its response to changes in setpoint and…
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Light is known to interact with matter in very specific ways, which may be exploited as a means of measuring…
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Linearity of Measurement Instruments The purpose of calibration is to ensure the input and output of an…
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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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The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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Volumes could be written about poor diagnostic technique. The following mistakes are not intended to comprise…
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In a manually-controlled process, a human operator directly actuates some form of final control element…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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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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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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Coy, John J. et. al. (December 2012) Sampled graphic illustrations from his NASA Reference Publication…
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Feedback obtained from industrial users of FF reveal a common pattern: Fieldbus is a powerful and reliable…
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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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The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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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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Most of these formulae appear in molecular chemical form rather than structural form. For example, ethanol…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…
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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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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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As a general rule, high achievement only takes place in an atmosphere of high expectations. Sometimes these…
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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 simplest classes of temperature sensor is one where temperature effects a change in electrical…
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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 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 most popular form of signal transmission used in modern industrial instrumentation systems (as of this…
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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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The final element of PID control is the “D” term, which stands for derivative. This is a calculus…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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A temperature switch is one detecting the temperature of some substance. Temperature switches often use…
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