Learning PLC programming is a very important skill. If your job involves programming, then you will likely…
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Learn about Modbus function codes, the structure of Modbus message packets, and the various types of channels used to transmit Modbus telegrams between controllers.
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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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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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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 vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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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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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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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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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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While the term “probability” may evoke images of imprecision, probability is in fact an exact…
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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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Hydrogen ion activity in aqueous (water-solvent) solutions is a very important parameter for a wide variety of…
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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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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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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Capacitive level instruments measure electrical capacitance of a conductive rod inserted vertically into a…
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In order to provide an interface between the internal (digital) world of a computer and the external (analog)…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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Solids tend to expand when heated. The amount that a solid sample will expand with increased temperature…
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By definition, a source is a device delivering energy into a system, while a load is a device extracting…
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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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Some analyzers measure the composition of a process stream by directly immersing the sensing element in that…
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Converting between disparate units of measurement is the bane of many science students. The problem is worse…
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As a general rule, high achievement only takes place in an atmosphere of high expectations. Sometimes these…
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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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A very common form of on/off valve used for pneumatic and hydraulic systems alike is the solenoid valve. A…
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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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In addition to Ohm’s Law, we have a set of rules describing how voltages, currents, and resistances…
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The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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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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A much simpler alternative to continuous vibration sensors (displacement or acceleration) and monitoring…
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One of the simplest classes of temperature sensor is one where temperature effects a change in electrical…
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A pressure switch is one that detects the presence of fluid pressure. Pressure switches often use diaphragms…
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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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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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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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Coy, John J. et. al. (December 2012) Sampled graphic illustrations from his NASA Reference Publication…
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A fluid is any substance having the ability to flow: to freely change shape and move under the influence of a…
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A fundamental principle in instrumentation system troubleshooting is that every instrument has at least one…
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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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An important performance parameter for transmitter instruments is something often referred to as turndown or…
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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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A whole class of problem-solving techniques focuses on altering the given problem into a simpler form that is…
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By definition, a source is a device delivering energy into a system, while a load is a device extracting…
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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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Electrical Resistance Resistance (\(R\)) is the dissipative opposition to an electric current, analogous to…
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Every flow-measuring instrument exploits a physical principle to measure the flow rate of fluid stream.…
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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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Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…
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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float directly sets…
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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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