DC electric current signals may also be used to communicate process measurement information from transmitters…
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The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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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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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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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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There is much to be said for neatness of assembly in electrical signal wiring. Even though the electrons…
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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 we have seen, the concept of differentiation is finding the rate-of-change of one variable compared to…
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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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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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Like many other mathematical operations, the derivative and the integral perform inverse operations from each…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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 flow switch is one that detects the flow of some fluid through a pipe. Flow switches often use…
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Imagine a major marathon race, where hundreds of runners gather in one place to compete. When the starting gun…
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Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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A machine in the broad sense of the word is any device designed to translate some form of energy into useful…
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An important legacy technology for all kinds of continuous measurement is the self-balancing system. A…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Some analyzers measure the composition of a process stream by directly immersing the sensing element in that…
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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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At the next OSI Reference Model layer (layer 4) is a set of protocols specifying how reliable communication…
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I remember first learning about the world-wide Internet, and wondering what it actually looked like. The first…
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Diagnostic ability is arguably the most difficult skill to develop within a student, and also the most…
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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 of our knowledge about atomic structure comes from experimental data relating the interaction between…
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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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Hydrogen ion activity in aqueous (water-solvent) solutions is a very important parameter for a wide variety of…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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“Radio” systems use electromagnetic fields to communicate information over long distances through…
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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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Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…
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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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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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A powerful mathematical concept useful for analyzing practically any physical system – electrical…
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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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Electrical Resistance Resistance (\(R\)) is the dissipative opposition to an electric current, analogous to…
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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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Some of the simplest types of digital communication networks found in industry are defined by the EIA…
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These fortifications focus on human behavior rather than system design or component selection. In some ways…
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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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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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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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To summarize some of the key points and concepts for teaching: Do not waste class time transmitting facts to…
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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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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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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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In addition to Ohm’s Law, we have a set of rules describing how voltages, currents, and resistances…
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Coy, John J. et. al. (December 2012) Sampled graphic illustrations from his NASA Reference Publication…
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Creative Commons Attribution 4.0 International Public License By exercising the Licensed Rights (defined…
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PID control can be a confusing concept to understand. Here, a brief summary of each term within PID (P. I, and…
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Much has been written about the benefits of robust PID control. Increased productivity, decreased equipment…
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