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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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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 addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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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A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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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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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…
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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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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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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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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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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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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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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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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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Layer 1 of the OSI Reference Model is where we define the “physical” elements of a digital data…
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Binary patterns are not just able to represent numerical values. Given a standardized code, they may represent…
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A powerful mathematical concept useful for analyzing practically any physical system – electrical…
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Mechanical pressure-sensing elements include the bellows, the diaphragm, and the bourdon tube. Each of these…
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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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To review, voltage is the measure of potential energy available to electric charges. Current is the uniform…
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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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The following animation shows the calculus concepts of differentiation and integration (with respect to time)…
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The Law of Mass Conservation states that matter can neither be created nor destroyed. The Law of Energy…
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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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Regardless of valve type, all stem-actuated control valves require some form of seal allowing motion of the…
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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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Converting between disparate units of measurement is the bane of many science students. The problem is worse…
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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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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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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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The following animation shows how a radio-energy pulse travels down and then up the waveguide of a guided-wave…
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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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When I began teaching full-time in 1998, most of what I thought I understood about good teaching was actually…
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