Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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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 great many chemical composition measurements may be made indirectly by means of electricity, if those…
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There are many process control applications in the industry where it is desirable to have multiple control…
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A temperature switch is one detecting the temperature of some substance. Temperature switches often use…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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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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As we have seen, the concept of differentiation is finding the rate-of-change of one variable compared to…
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A wise PLC programmer once told me that the first thing any aspiring programmer should learn about the PLC…
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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 disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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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 term “grid” refers to the conductors and equipment interconnecting power sources to power…
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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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Light is known to interact with matter in very specific ways, which may be exploited as a means of measuring…
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In our first signal characterization example, we tackle the problem of measuring fluid flow through a pipe. To…
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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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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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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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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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Perhaps the most confusing aspect of discrete sensors is the definition of a sensor’s normal status.…
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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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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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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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DC electric current signals may also be used to communicate process measurement information from transmitters…
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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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Some of the simplest types of digital communication networks found in industry are defined by the EIA…
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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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Sensors used to measure vibration come in three basic types: displacement, velocity, and acceleration.…
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Certain types of nuclear radiation easily penetrates the walls of industrial vessels, but is attenuated by…
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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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The vast majority of modern process transmitters (both analog and digital) come equipped with a feature known…
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Like many other mathematical operations, the derivative and the integral perform inverse operations from each…
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A hand switch is exactly what the name implies: an electrical switch actuated by a person’s hand motion.…
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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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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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Fluid pressure exerts force on any surface area it contacts, as described by the formula \(F = PA\). One…
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Electrical Resistance Resistance (\(R\)) is the dissipative opposition to an electric current, analogous to…
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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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Visualizing the actions of P, I, and D tuning parameters using graphs is extremely useful in predicting the…
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An interesting parallel to the “unity fraction” unit conversion technique is something referred to…
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One of the most common, and most useful, pressure measuring instruments in industry is the differential…
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The fundamental principle of electromagnetism is that an electric current will create a magnetic field at…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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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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The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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Self-balancing mechanisms consisting solely of a baffle/nozzle detector coupled to a feedback bellows, while…
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A different strategy for controlling the flow of fluid is to insert a rotary element into the flow path.…
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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 unique form of technical diagram for describing the abstract functions comprising a control system (e.g. PID…
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Perhaps the simplest form of solid or liquid level measurement is with a float: a device that rides on the…
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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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The majority of flowmeter technologies operate on the principle of interpreting fluid flow based on the…
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Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose…
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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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The key to understanding how three-phase electric motors work is to have an accurate mental picture of the…
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The following collection of photographs chronicles the complete disassembly of a Fisher E-body globe valve…
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Feedback obtained from industrial users of FF reveal a common pattern: Fieldbus is a powerful and reliable…
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