The efficient identification and correction of instrument calibration errors is an important function for…
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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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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. 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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Any physical location in an industrial facility harboring the potential of explosion due to the presence of…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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An engineer named Bob Metcalfe conceived the idea of Ethernet in 1973, while working for the Xerox research…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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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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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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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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Valves can experience a number of problems, most of them either preventable or repairable. These problems can…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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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 simple control system drawn in block diagram form looks like this: Information from the measuring device…
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Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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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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The Law of Continuity for fluids states that the product of mass density (\(\rho\)), cross-sectional pipe area…
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In order for any PID controller to be practical, it must be able to do more than just implement the PID…
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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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As we have seen, feedforward control is a way to improve the stability of a feedback control system in the…
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Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…
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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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Diagnostic ability is arguably the most difficult skill to develop within a student, and also the most…
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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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A flow switch is one detecting the flow of some fluid through a pipe. Flow switches often use…
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In order to provide an interface between the internal (digital) world of a computer and the external (analog)…
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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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PID control can be a confusing concept to understand. Here, a brief summary of each term within PID (P. I, and…
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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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A powerful mathematical concept useful for analyzing practically any physical system – electrical…
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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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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The efficient identification and correction of instrument calibration errors is an important function for…
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To understand just how different FOUNDATION Fieldbus is from other digital instrument systems, consider a…
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Hydrogen ion activity in aqueous (water-solvent) solutions is a very important parameter for a wide variety 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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The most popular form of signal transmission used in modern industrial instrumentation systems (as of this…
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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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At the next OSI Reference Model layer (layer 4) is a set of protocols specifying how reliable communication…
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Sometimes we encounter a diversity of instrument signal standards in one control system. Such is the case with…
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A 4 to 20 mA current signal represents some signal along a 0 to 100 percent scale. Usually, this scale is…
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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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A design-based fortification is one rooted in technical details of system architecture and functionality. Some…
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Most of these formulae appear in molecular chemical form rather than structural form. For example, ethanol…
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When a high-energy photon strikes an atom, it may eject one of the lower-level electrons from its shell,…
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Once while working as an instrument technician in an aluminum foundry, a mechanic asked me what it was that I…
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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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The following animation shows a rotating phasor in three-dimensional form. The phasor rotates in a complex…
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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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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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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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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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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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It is possible to convey electrical power and communicate analog information over the same two wires using 4…
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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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Shown here is a partial listing of principles applied in the subject matter of this chapter, given for the…
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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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