I remember first learning about the world-wide Internet, and wondering what it actually looked like. The first…
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In a manually-controlled process, a human operator directly actuates some form of final control element…
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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…
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There are multiple motives for compromising the security of an industrial control system, some of which…
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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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A design-based fortification is one rooted in technical details of system architecture and functionality. Some…
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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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Cyber-security seems to have its own vocabulary, ranging from unwieldy technical acronyms to slang terms…
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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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Light has long been used as a long-range signaling medium. While communication by light through open air is…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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These fortifications focus on human behavior rather than system design or component selection. In some ways…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing 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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Imagine a major marathon race, where hundreds of runners gather in one place to compete. When the starting gun…
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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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A completely different way of measuring liquid level in vessels is to bounce a traveling wave off the surface…
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An exciting development in industrial instrumentation is the WirelessHART radio communication standard,…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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“As to methods there may be a million and then some, but principles are few. The man who grasps…
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To understand just how different FOUNDATION Fieldbus is from other digital instrument systems, consider a…
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Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…
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Self-balancing mechanisms consisting solely of a baffle/nozzle detector coupled to a feedback bellows, while…
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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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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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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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A positive displacement flowmeter is a cyclic mechanism built to pass a fixed volume of fluid through with…
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To show a practical process example, let’s examine three diagrams for a compressor control system,…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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Any conductor possesses a characteristic called inductance: the ability to store energy in the form of a…
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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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An important design parameter of a control valve is the position it will “fail” to if it loses…
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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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There are multiple motives for compromising the security of an industrial control system, some of which…
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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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Much has been written about the benefits of robust PID control. Increased productivity, decreased equipment…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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