Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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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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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known 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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Valves can experience a number of problems, most of them either preventable or repairable. These problems can…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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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 Law of Continuity for fluids states that the product of mass density (\(\rho\)), cross-sectional pipe area…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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Although analog electronic process controllers are considered a newer technology than pneumatic process…
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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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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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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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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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The transformer is one of the most important components in all of AC circuitry. Principally used to…
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The efficient identification and correction of instrument calibration errors is an important function for…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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A variety of technologies exist to measure the quantity of stored material in a vessel. For liquid…
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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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This section shows some of the many instrument symbols found in different types of technical diagrams used to…
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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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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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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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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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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 special type flowmeter suited for powdered or granular solids is the weighfeeder. One of the most common…
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A unique form of differential pressure-based flow measurement deserves its own section in this flow…
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A laser is a light source emitting waves of light that not only share the exact same frequency (color)…
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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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The dispersion of visible light into its constituent colors goes all the way back to the 17th century with…
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A great many precision instruments use the principle of balance to measure some quantity. Perhaps the simplest…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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Lipták, Béla G. et al., Instrument Engineers’ Handbook – Process Measurement and Analysis Volume I,…
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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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