Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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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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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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In a manually-controlled process, a human operator directly actuates some form of final control element…
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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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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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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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A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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Light is known to interact with matter in very specific ways, which may be exploited as a means of measuring…
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A fundamental principle in instrumentation system troubleshooting is that every instrument has at least one…
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One very convenient feature of waves is that their properties are universal. Waves of water in the ocean,…
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Any physical location in an industrial facility harboring the potential of explosion due to the presence of…
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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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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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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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A chemical reaction resulting in a net release of energy is called exothermic. Conversely, a chemical reaction…
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Many years ago, when I was first learning about electricity, I happened to discover a length of coaxial…
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Much of our knowledge about atomic structure comes from experimental data relating the interaction between…
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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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A chemical reaction resulting in a net release of energy is called exothermic. Conversely, a chemical reaction…
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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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One of the marks of a successful problem-solver is a habit of applying general principles to every new problem…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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Stoichiometry is the accounting of atoms before and after a chemical reaction. It is an expression of the Law…
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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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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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Take for instance the problem of measuring fluid flow through a pipe. To the layperson, this may seem to be a…
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To understand just how different FOUNDATION Fieldbus is from other digital instrument systems, consider a…
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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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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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Sometimes we encounter a diversity of instrument signal standards in one control system. Such is the case with…
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A unique form of technical diagram for describing the abstract functions comprising a control system (e.g. PID…
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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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Learning from reading printed text is a kind of problem-solving activity it is own right. The problem is how…
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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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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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The concepts of calibration (trimming) and ranging are often difficult for new students of instrumentation to…
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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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