An important design parameter of a control valve is the position it will “fail” to if it loses…
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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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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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A completely different way of measuring liquid level in vessels is to bounce a traveling wave off the surface…
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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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Any conductor possesses a characteristic called inductance: the ability to store energy in the form of a…
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“Radio” systems use electromagnetic fields to communicate information over long distances through…
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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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Tube, like pipe, is a hollow structure designed to provide an enclosed pathway for fluids to flow. In the case…
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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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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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The efficient identification and correction of instrument calibration errors is an important function for…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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A quantitative PID tuning procedure is a step-by-step approach leading directly to a set of numerical values…
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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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Light has long been used as a long-range signaling medium. While communication by light through open air is…
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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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As we have seen, the concept of integration is finding the accumulation of one variable multiplied by another…
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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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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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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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Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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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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The vast majority of modern process transmitters (both analog and digital) come equipped with a feature known…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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Diagnostic ability is arguably the most difficult skill to develop within a student, and also the most…
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Volumes could be written about poor diagnostic technique. The following mistakes are not intended to comprise…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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Much of our knowledge about atomic structure comes from experimental data relating the interaction between…
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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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Imagine a major marathon race, where hundreds of runners gather in one place to compete. When the starting gun…
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Valves can experience a number of problems, most of them either preventable or repairable. These problems can…
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Suppose we wished to measure the rate of propane gas flow through a hose to a torch: Flowmeters appropriate…
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Many traditional flowmeter technologies respond to the volumetric flow rate of the moving fluid.…
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To show a practical process example, let’s examine three diagrams for a compressor control system,…
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The dispersion of visible light into its constituent colors goes all the way back to the 17th century with…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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In contrast to quantitative tuning procedures where definite numerical values for P, I, and D controller…
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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 completely different way of measuring liquid level in vessels is to bounce a traveling wave off the surface…
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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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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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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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A pressure switch is one detecting the presence of fluid pressure. Pressure switches often use diaphragms or…
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Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose…
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DC electric current signals may also be used to communicate process measurement information from transmitters…
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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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An important performance parameter for transmitter instruments is something often referred to as turndown or…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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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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The next level of detail is the Process and Instrument Diagram, or P&ID. Here, we see a “zooming…
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