Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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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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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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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 simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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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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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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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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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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A chemical reaction resulting in a net release of energy is called exothermic. Conversely, a chemical reaction…
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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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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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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 number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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What is Calibration? To calibrate an instrument means to check and adjust (if necessary) its response so the…
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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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To summarize some of the key points and concepts for teaching: Do not waste class time transmitting facts to…
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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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Fluid pressure exerts force on any surface area it contacts, as described by the formula \(F = PA\). One…
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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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It is possible to convey electrical power and communicate analog information over the same two wires using 4…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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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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Impedance in a series circuit is the orthogonal sum of resistance and reactance: \[Z = \sqrt{R^2 + (X_L -…
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Filled-bulb systems exploit the principle of fluid expansion to measure temperature. If a fluid is enclosed in…
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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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The final step in treating wastewater before releasing it into the natural environment is to kill any harmful…
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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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