Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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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 purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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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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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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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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Using filter cells to eliminate wavelengths associated with interfering gases is called positive filtering in…
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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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For better or worse, there are no fewer than three different forms of PID equations implemented in modern PID…
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An on/off valve is the fluid equivalent of an electrical switch: a device that either allows unimpeded flow or…
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A flow switch is one detecting the flow of some fluid through a pipe. Flow switches often use…
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A form of protection against faults on long-distance power lines is called distance relaying, so named because…
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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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As we have seen, feedforward control is a way to improve the stability of a feedback control system in the…
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An interesting parallel to the “unity fraction” unit conversion technique is something referred to…
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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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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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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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In reliability engineering, it is important to be able to quantity the reliability (or conversely, the…
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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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A hand switch is exactly what the name implies: an electrical switch actuated by a person’s hand motion.…
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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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A very common method for directly controlling low flow rates of fluids is to use a device known as a metering…
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To understand just how different FOUNDATION Fieldbus is from other digital instrument systems, consider a…
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DC electric current signals may also be used to communicate process measurement information from transmitters…
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Feedback obtained from industrial users of FF reveal a common pattern: Fieldbus is a powerful and reliable…
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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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Filled-bulb systems exploit the principle of fluid expansion to measure temperature. If a fluid is enclosed in…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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pH is the measurement of the hydrogen ion activity in a liquid solution. It is one of the most common forms of…
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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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Electrical Resistance Resistance (\(R\)) is the dissipative opposition to an electric current, analogous to…
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There is much to be said for neatness of assembly in electrical signal wiring. Even though the electrons…
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A very simple device used to measure pressure is the manometer: a fluid-filled tube where an applied gas…
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In reliability engineering, it is important to be able to quantity the reliability (or conversely, the…
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Every flow-measuring instrument exploits a physical principle to measure the flow rate of fluid stream.…
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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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When control valves operate between fully open and fully shut, they serve much the same purpose in process…
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The advent of “smart” field instruments containing microprocessors has been a great advance for…
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As a general rule, high achievement only takes place in an atmosphere of high expectations. Sometimes these…
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An on/off valve is the fluid equivalent of an electrical switch: a device that either allows unimpeded flow or…
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A special type flowmeter suited for powdered or granular solids is the weighfeeder. One of the most common…
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An variable-area flowmeter is one where the fluid must pass through a restriction whose area increases with…
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An important design parameter of a control valve is the position it will “fail” to if it loses…
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