While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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Data-processing modules within FF systems are known as function blocks. Sometimes these blocks serve merely to…
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Learning PLC programming is a very important skill. If your job involves programming, then you will likely…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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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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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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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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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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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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Imagine a major marathon race, where hundreds of runners gather in one place to compete. When the starting gun…
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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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One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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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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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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 two “process variables” we rely on most heavily in the field of electrical measurement and…
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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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An important performance parameter for transmitter instruments is something often referred to as turndown or…
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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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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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Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose…
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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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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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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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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing 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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Classical mechanics (often called Newtonian mechanics in honor of Isaac Newton) deal with forces and motions…
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A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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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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Light is known to interact with matter in very specific ways, which may be exploited as a means of measuring…
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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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Sample sizes of chemical substances are often measured in moles. One mole of a substance is defined as a…
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Electrical power grids primarily consist of three-phase AC circuits. This means most power lines (transmission…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Suppose we wished to measure the rate of propane gas flow through a hose to a torch: Flowmeters appropriate…
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Once while working as an instrument technician in an aluminum foundry, a mechanic asked me what it was that I…
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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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Capacitive level instruments measure electrical capacitance of a conductive rod inserted vertically into a…
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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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A chemical reaction resulting in a net release of energy is called exothermic. Conversely, a chemical reaction…
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Sensors used to measure vibration come in three basic types: displacement, velocity, and acceleration.…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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The final element of PID control is the “D” term, which stands for derivative. This is a calculus…
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The advent of “smart” field instruments containing microprocessors has been a great advance for…
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Few areas of mathematics are as powerfully useful in describing and analyzing the physical world as calculus:…
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An exciting development in industrial instrumentation is the WirelessHART radio communication standard,…
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Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…
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All substances are comprised of various elements in various combinations and proportions. Elements may thus be…
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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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First, let us review some of the properties of differentials and derivatives, referencing the expression and…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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The very purpose of physics is to quantitatively describe and explain the physical world in as few terms as…
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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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Filled-bulb systems exploit the principle of fluid expansion to measure temperature. If a fluid is enclosed in…
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