The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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The Law of Continuity for fluids states that the product of mass density (\(\rho\)), cross-sectional pipe area…
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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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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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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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As we have seen, the concept of integration is finding the accumulation of one variable multiplied by another…
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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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As previously defined, calibration refers to the checking and adjustment of an instrument so that its output…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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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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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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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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Capacitive level instruments measure electrical capacitance of a conductive rod inserted vertically into a…
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“Radio” systems use electromagnetic fields to communicate information over long distances through…
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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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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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The very purpose of physics is to quantitatively describe and explain the physical world in as few terms as…
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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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It is often useful to express the amplitude of an alternating quantity such as voltage or current in terms…
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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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Perhaps the simplest form of solid or liquid level measurement is with a float: a device that rides on the…
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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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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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Some analyzers measure the composition of a process stream by directly immersing the sensing element in that…
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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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In contrast to quantitative tuning procedures where definite numerical values for P, I, and D controller…
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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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Light is known to interact with matter in very specific ways, which may be exploited as a means of measuring…
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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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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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As we have seen, feedforward control is a way to improve the stability of a feedback control system in the…
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