As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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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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The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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A very common form of on/off valve used for pneumatic and hydraulic systems alike is the solenoid valve. A…
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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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Converting between disparate units of measurement is the bane of many science students. The problem is worse…
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Abdelaziz, Ahmed (June 2014) Identified numerous typographical errors throughout the book, mostly repeated…
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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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While the term “probability” may evoke images of imprecision, probability is in fact an exact…
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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 addition to Ohm’s Law, we have a set of rules describing how voltages, currents, and resistances…
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In order for any PID controller to be practical, it must be able to do more than just implement the PID…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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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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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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Level gauges are perhaps the simplest indicating instrument for liquid level in a vessel. They are often found…
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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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Most people reading this book have likely had the experience of adjusting water temperature using two hand…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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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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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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Volumes could be written about poor diagnostic technique. The following mistakes are not intended to comprise…
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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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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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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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In some process applications, it is important that the control valve be able to completely stop fluid flow…
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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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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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Valves can experience a number of problems, most of them either preventable or repairable. These problems can…
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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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Control valves are supposed to deliver reliable, repeatable control of process fluid flow rate over a wide…
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The Law of Continuity for fluids states that the product of mass density (\(\rho\)), cross-sectional pipe area…
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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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Filled-bulb systems exploit the principle of fluid expansion to measure temperature. If a fluid is enclosed in…
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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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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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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An variable-area flowmeter is one where the fluid must pass through a restriction whose area increases with…
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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 legacy technology for all kinds of continuous measurement is the self-balancing system. A…
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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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Some self-powered (4-wire) analog electronic transmitters are designed to behave as electrical loads rather…
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Using filter cells to eliminate wavelengths associated with interfering gases is called positive filtering in…
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The Law of Continuity for fluids states that the product of mass density (\(\rho\)), cross-sectional pipe area…
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Suppose we wished to measure the consumption of propane over time for a large propane storage tank supplying a…
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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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PID control can be a confusing concept to understand. Here, a brief summary of each term within PID (P. I, and…
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Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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Calculus has a reputation for being difficult to learn, and with good reason. The traditional approach to…
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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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Some of the simplest types of digital communication networks found in industry are defined by the EIA…
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One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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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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As a general rule, high achievement only takes place in an atmosphere of high expectations. Sometimes these…
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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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