Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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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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A whole class of problem-solving techniques focuses on altering the given problem into a simpler form that is…
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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 technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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Much has been written about the benefits of robust PID control. Increased productivity, decreased equipment…
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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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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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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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This section does not describe a particular type of flowmeter, but rather a design that may be implemented for…
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Area refers to the size of two-dimensional surface. Volume refers to the size of a three-dimensional space. To…
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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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All masses require force to accelerate (we can also think of this in terms of the mass generating a reaction…
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One of the great benefits of digital technology is the ability to communicate vast amounts of information over…
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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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The following photograph shows a large air blower in a wastewater treatment facility equipped with a…
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Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…
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A temperature switch is one detecting the temperature of some substance. Temperature switches often use…
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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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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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Electrical Resistance Resistance (\(R\)) is the dissipative opposition to an electric current, analogous to…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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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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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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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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A limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…
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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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A fundamental limitation of proportional control has to do with its response to changes in setpoint and…
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The advent of “smart” field instruments containing microprocessors has been a great advance for…
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It is often useful to express the amplitude of an alternating quantity such as voltage or current in terms…
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An engineer named Bob Metcalfe conceived the idea of Ethernet in 1973, while working for the Xerox research…
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Volumes could be written about poor diagnostic technique. The following mistakes are not intended to comprise…
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In some process applications, it is important that the control valve be able to completely stop fluid flow…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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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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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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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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Linearity of Measurement Instruments The purpose of calibration is to ensure the input and output of 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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One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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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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Any power grid large enough to meet the demand of an entire nation must have multiple generators drawing from…
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“Radio” systems use electromagnetic fields to communicate information over long distances through…
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Light has long been used as a long-range signaling medium. While communication by light through open air is…
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Perhaps the simplest form of solid or liquid level measurement is with a float: a device that rides on the…
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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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Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…
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A powerful mathematical concept useful for analyzing practically any physical system – electrical…
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Learning from reading printed text is a kind of problem-solving activity it is own right. The problem is how…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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Labwork is an essential part of any science-based curriculum. Here, much improvement may be made over the…
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Flow, by definition, is the passage of material from one location to another over time. So far this chapter…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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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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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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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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A special type flowmeter suited for powdered or granular solids is the weighfeeder. One of the most common…
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