A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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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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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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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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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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There is much to be said for neatness of assembly in electrical signal wiring. Even though the electrons…
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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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Steam boilers are very common in industry, principally because steam power is so useful. Common uses for steam…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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A variety of problem-solving techniques have been presented for students over the years which are all helpful…
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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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This animation shows the basic operation of a gas chromatograph, showing the separation of different molecular…
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The concepts of calibration (trimming) and ranging are often difficult for new students of instrumentation to…
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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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Any physical location in an industrial facility harboring the potential of explosion due to the presence of…
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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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Tube, like pipe, is a hollow structure designed to provide an enclosed pathway for fluids to flow. In the case…
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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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Atom: the smallest unit of matter that may be isolated by chemical means. Particle: a part of an atom,…
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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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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…
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Shown here is a partial listing of principles applied in the subject matter of this chapter, given for the…
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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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Many years ago, when I was first learning about electricity, I happened to discover a length of coaxial…
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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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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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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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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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An important performance parameter for transmitter instruments is something often referred to as turndown or…
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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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To summarize some of the key points and concepts for teaching: Do not waste class time transmitting facts to…
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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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The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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The three “elementary” particles of matter comprising all atoms are electrons, protons, and…
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Hydrogen ion activity in aqueous (water-solvent) solutions is a very important parameter for a wide variety of…
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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…
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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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