A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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 simple control system drawn in block diagram form looks like this: Information from the measuring device…
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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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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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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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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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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 purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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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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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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Much has been written about the benefits of robust PID control. Increased productivity, decreased equipment…
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Certain types of nuclear radiation easily penetrates the walls of industrial vessels, but is attenuated by…
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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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The final element of PID control is the “D” term, which stands for derivative. This is a calculus…
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At the root of successful system diagnosis is a rigorous adherence to scientific reasoning. There exists no…
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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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An interesting parallel to the “unity fraction” unit conversion technique is something referred to…
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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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The dispersion of visible light into its constituent colors goes all the way back to the 17th century with…
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In November of 2007 a new computer virus was submitted to a virus scanning service. The purpose of this new…
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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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Perhaps the most important rule to obey when using pneumatic instruments is to maintain clean and dry…
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To understand just how different FOUNDATION Fieldbus is from other digital instrument systems, consider a…
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An important performance parameter for transmitter instruments is something often referred to as turndown or…
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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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A temperature switch is one detecting the temperature of some substance. Temperature switches often use…
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Learning PLC programming is a very important skill. If your job involves programming, then you will likely…
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Some problem-solving techniques are unique to quantitative problems, involving mathematical calculations. In…
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