Solids tend to expand when heated. The amount that a solid sample will expand with increased temperature…
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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 laser is a light source emitting waves of light that not only share the exact same frequency (color)…
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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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Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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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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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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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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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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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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Most people reading this book have likely had the experience of adjusting water temperature using two hand…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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An important design parameter of a control valve is the position it will “fail” to if it loses…
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The efficient identification and correction of instrument calibration errors is an important function for…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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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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Since we often use electricity to convey energy from one location to another, it is important to be able to…
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Thermodynamics is the study of heat, temperature, and their related effects in physical systems. As a subject,…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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In reliability engineering, it is important to be able to quantity the reliability (or conversely, the…
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This animation shows the basic operation of a gas chromatograph, showing the separation of different molecular…
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While the term “probability” may evoke images of imprecision, probability is in fact an exact…
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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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Fluid pressure exerts force on any surface area it contacts, as described by the formula \(F = PA\). One…
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Every flow-measuring instrument exploits a physical principle to measure the flow rate of fluid stream.…
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Mechanical pressure-sensing elements include the bellows, the diaphragm, and the bourdon tube. Each of these…
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What is Calibration? To calibrate an instrument means to check and adjust (if necessary) its response so the…
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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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When a high-energy photon strikes an atom, it may eject one of the lower-level electrons from its shell,…
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pH is the measurement of the hydrogen ion activity in a liquid solution. It is one of the most common forms of…
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Learning how to tune PID controllers is a skill born of much practice. Regardless of how thoroughly you may…
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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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Weight-based level instruments sense process level in a vessel by directly measuring the weight of the vessel.…
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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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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 electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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A limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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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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This section shows some of the many instrument symbols found in different types of technical diagrams used to…
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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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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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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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Self-balancing mechanisms consisting solely of a baffle/nozzle detector coupled to a feedback bellows, while…
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As a general rule, high achievement only takes place in an atmosphere of high expectations. Sometimes these…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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Many liquid substances undergo a process whereby their constituent molecules split into positively and…
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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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An on/off valve is the fluid equivalent of an electrical switch: a device that either allows unimpeded flow or…
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First, let us review some of the properties of differentials and derivatives, referencing the expression and…
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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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Linearity of Measurement Instruments The purpose of calibration is to ensure the input and output of an…
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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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Capacitive level instruments measure electrical capacitance of a conductive rod inserted vertically into a…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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