Up until this point, we have explored various types of instrumentation diagram, each one making reference to…
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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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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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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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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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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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Regardless of valve type, all stem-actuated control valves require some form of seal allowing motion of the…
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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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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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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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A whole class of problem-solving techniques focuses on altering the given problem into a simpler form that is…
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Much has been written about the benefits of robust PID control. Increased productivity, decreased equipment…
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Most people reading this book have likely had the experience of adjusting water temperature using two hand…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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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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One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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Most pneumatic instruments use a simple but highly sensitive mechanism for converting mechanical motion into…
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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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When a high-energy photon strikes an atom, it may eject one of the lower-level electrons from its shell,…
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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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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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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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It is possible to convey electrical power and communicate analog information over the same two wires using 4…
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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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By definition, a source is a device delivering energy into a system, while a load is a device extracting…
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Like many other mathematical operations, the derivative and the integral perform inverse operations from each…
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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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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The fundamental principle of electromagnetism is that an electric current will create a magnetic field at…
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Up until this point, we have explored various types of instrumentation diagram, each one making reference 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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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Although analog electronic process controllers are considered a newer technology than pneumatic process…
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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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In some process applications, it is important that the control valve be able to completely stop fluid flow…
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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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One very convenient feature of waves is that their properties are universal. Waves of water in the ocean,…
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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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Measuring the flow rate of liquid through an open channel is not unlike measuring the flow rate of a liquid…
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For better or worse, there are no fewer than three different forms of PID equations implemented in modern PID…
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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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Many liquid substances undergo a process whereby their constituent molecules split into positively and…
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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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An important legacy technology for all kinds of continuous measurement is the self-balancing system. A…
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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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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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A level switch is one detecting the level of liquid or solid (granules or powder) in a vessel. Level switches…
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The following animation shows a rotating phasor in three-dimensional form. The phasor rotates in a complex…
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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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Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…
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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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Calculus. Few areas of mathematics are as powerfully useful in describing and analyzing the physical…
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Regardless of valve type, all stem-actuated control valves require some form of seal allowing motion of the…
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