One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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As we have seen, the concept of integration is finding the accumulation of one variable multiplied by another…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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Like many other mathematical operations, the derivative and the integral perform inverse operations from each…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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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 different strategy for controlling the flow of fluid is to insert a rotary element into the flow path.…
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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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In reliability engineering, it is important to be able to quantity the reliability (or conversely, the…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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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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A wise PLC programmer once told me that the first thing any aspiring programmer should learn about the PLC…
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The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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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 confusing aspect of discrete sensors is the definition of a sensor’s normal status.…
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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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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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One very convenient feature of waves is that their properties are universal. Waves of water in the ocean,…
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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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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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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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One of the most common, and most useful, pressure measuring instruments in industry is the differential…
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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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Much has been written about the benefits of robust PID control. Increased productivity, decreased equipment…
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Coy, John J. et. al. (December 2012) Sampled graphic illustrations from his NASA Reference Publication…
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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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In November of 2007 a new computer virus was submitted to a virus scanning service. The purpose of this new…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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Classical mechanics (often called Newtonian mechanics in honor of Isaac Newton) deal with forces and motions…
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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 final step in treating wastewater before releasing it into the natural environment is to kill any harmful…
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Area refers to the size of two-dimensional surface. Volume refers to the size of a three-dimensional space. To…
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(Will be addressed in future versions of this book)
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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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One of the marks of a successful problem-solver is a habit of applying general principles to every new problem…
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It is often useful to express the amplitude of an alternating quantity such as voltage or current in terms…
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The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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