Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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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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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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 completely different way of measuring liquid level in vessels is to bounce a traveling wave off the surface…
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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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Control valves are supposed to deliver reliable, repeatable control of process fluid flow rate over a wide…
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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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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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A limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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Coy, John J. et. al. (December 2012) Sampled graphic illustrations from his NASA Reference Publication…
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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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Once while working as an instrument technician in an aluminum foundry, a mechanic asked me what it was that I…
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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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Finally, we arrive at the loop diagram (sometimes called a loop sheet) for the compressor surge control system…
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Suppose we wished to measure the consumption of propane over time for a large propane storage tank supplying a…
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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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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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Some self-powered (4-wire) analog electronic transmitters are designed to behave as electrical loads rather…
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