All masses require force to accelerate (we can also think of this in terms of the mass generating a reaction…
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As previously defined, calibration refers to the checking and adjustment of an instrument so that its output…
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Binary patterns are not just able to represent numerical values. Given a standardized code, they may represent…
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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 different strategy for controlling the flow of fluid is to insert a rotary element into the flow path.…
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In November of 2007 a new computer virus was submitted to a virus scanning service. The purpose of this new…
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A fundamental principle in instrumentation system troubleshooting is that every instrument has at least one…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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At the next OSI Reference Model layer (layer 4) is a set of protocols specifying how reliable communication…
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Like so many other industrial data networks, FOUNDATION Fieldbus is an “unswitched” or…
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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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A machine in the broad sense of the word is any device designed to translate some form of energy into useful…
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A vertical column of fluid generates a pressure at the bottom of the column owing to the action of gravity on…
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Stoichiometry is the accounting of atoms before and after a chemical reaction. It is an expression of the Law…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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Control valves are supposed to deliver reliable, repeatable control of process fluid flow rate over a wide…
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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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Self-balancing mechanisms consisting solely of a baffle/nozzle detector coupled to a feedback bellows, while…
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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float directly sets…
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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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Another category of control strategies involves the use of signal relays or function blocks with the ability…
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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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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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Current is the name we give to the motion of electric charges from a point of high potential to a point of low…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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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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As we have seen, feedforward control is a way to improve the stability of a feedback control system in the…
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Diagnostic ability is arguably the most difficult skill to develop within a student, and also the most…
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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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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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A very simple device used to measure pressure is the manometer: a fluid-filled tube where an applied gas…
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A fundamental limitation of proportional control has to do with its response to changes in setpoint and…
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When a high-energy photon strikes an atom, it may eject one of the lower-level electrons from its shell,…
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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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A completely different way of measuring liquid level in vessels is to bounce a traveling wave off the surface…
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Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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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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Fieldbus devices require far more attention in their initial setup and commissioning than their analog…
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A vertical column of fluid generates a pressure at the bottom of the column owing to the action of gravity on…
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DC electric current signals may also be used to communicate process measurement information from transmitters…
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Coy, John J. et. al. (December 2012) Sampled graphic illustrations from his NASA Reference Publication…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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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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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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A damper (otherwise known as a louvre) is a multi-element flow control device generally used to throttle large…
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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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There are many process control applications in the industry where it is desirable to have multiple control…
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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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One of the marks of a successful problem-solver is a habit of applying general principles to every new problem…
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To show a practical process example, let’s examine three diagrams for a compressor control system,…
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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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The majority of flowmeter technologies operate on the principle of interpreting fluid flow based on the…
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