The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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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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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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Regardless of valve type, all stem-actuated control valves require some form of seal allowing motion of the…
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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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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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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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Measuring the flow rate of liquid through an open channel is not unlike measuring the flow rate of a liquid…
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The fundamental principle of electromagnetism is that an electric current will create a magnetic field at…
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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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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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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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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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It is often useful to express the amplitude of an alternating quantity such as voltage or current in terms…
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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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One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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One of the great benefits of digital technology is the ability to communicate vast amounts of information over…
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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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In reliability engineering, it is important to be able to quantity the reliability (or conversely, the…
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(Will be addressed in future versions of this book)
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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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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Perhaps the simplest form of solid or liquid level measurement is with a float: a device that rides on the…
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Another category of control strategies involves the use of signal relays or function blocks with the ability…
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A flow switch is one that detects the flow of some fluid through a pipe. Flow switches often use…
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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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Most pneumatic instruments use a simple but highly sensitive mechanism for converting mechanical motion into…
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Pipe is a hollow structure designed to provide an enclosed pathway for fluids to flow, usually manufactured…
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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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Measuring the flow rate of liquid through an open channel is not unlike measuring the flow rate of a liquid…
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Impedance in a series circuit is the orthogonal sum of resistance and reactance: \[Z = \sqrt{R^2 + (X_L -…
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The transformer is one of the most important components in all of AC circuitry. Principally used to…
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Much has been written about the benefits of robust PID control. Increased productivity, decreased equipment…
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Fieldbus devices require far more attention in their initial setup and commissioning than their analog…
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These fortifications focus on human behavior rather than system design or component selection. In some ways…
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pH is the measurement of the hydrogen ion activity in a liquid solution. It is one of the most common forms of…
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Capacitive level instruments measure electrical capacitance of a conductive rod inserted vertically into a…
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One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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One of the great benefits of digital technology is the ability to communicate vast amounts of information over…
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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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Converting between disparate units of measurement is the bane of many science students. The problem is worse…
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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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This section shows some of the many instrument symbols found in different types of technical diagrams used to…
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A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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In a manually-controlled process, a human operator directly actuates some form of final control element…
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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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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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In modern industry, the most popular form of field-level signal transmission for variable industrial…
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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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The advent of “smart” field instruments containing microprocessors has been a great advance for…
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One of the marks of a successful problem-solver is a habit of applying general principles to every new problem…
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Learning is not merely a process of information transfer. It is first and foremost a transformation of…
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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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Earlier in this chapter you were shown a model of a nitrogen atom with a dense nucleus (comprised of protons…
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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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Much has been written about the benefits of robust PID control. Increased productivity, decreased equipment…
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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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