To show a practical process example, let’s examine three diagrams for a compressor control system,…
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A limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…
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Pipe is a hollow structure designed to provide an enclosed pathway for fluids to flow, usually manufactured…
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Many traditional flowmeter technologies respond to the volumetric flow rate of the moving fluid.…
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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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Most pneumatic instruments use a simple but highly sensitive mechanism for converting mechanical motion into…
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Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…
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Modern analog-to-digital converters are phenomenally accurate, dependable, repeatable, and surprisingly…
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Some analyzers measure the composition of a process stream by directly immersing the sensing element in that…
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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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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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One of the great benefits of digital technology is the ability to communicate vast amounts of information over…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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Suppose we wished to measure the rate of propane gas flow through a hose to a torch: Flowmeters appropriate…
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Mechanical pressure-sensing elements include the bellows, the diaphragm, and the bourdon tube. Each of these…
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Much has been written about the benefits of robust PID control. Increased productivity, decreased equipment…
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Feedback obtained from industrial users of FF reveal a common pattern: Fieldbus is a powerful and reliable…
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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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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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Light has long been used as a long-range signaling medium. While communication by light through open air is…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Diagnostic ability is arguably the most difficult skill to develop within a student, and also the most…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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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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The efficient identification and correction of instrument calibration errors is an important function for…
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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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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’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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The advent of “smart” field instruments containing microprocessors has been a great advance for…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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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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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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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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To review, voltage is the measure of potential energy available to electric charges. Current is the uniform…
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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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Lipták, Béla G. et al., Instrument Engineers’ Handbook – Process Measurement and Analysis Volume I,…
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Imagine a major marathon race, where hundreds of runners gather in one place to compete. When the starting gun…
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Using filter cells to eliminate wavelengths associated with interfering gases is called positive filtering in…
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A great many precision instruments use the principle of balance to measure some quantity. Perhaps the simplest…
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Sometimes we encounter a diversity of instrument signal standards in one control system. Such is the case with…
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In modern industry, the most popular form of field-level signal transmission for variable industrial…
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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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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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An interesting parallel to the “unity fraction” unit conversion technique is something referred to…
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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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To understand just how different FOUNDATION Fieldbus is from other digital instrument systems, consider a…
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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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Learning from reading printed text is a kind of problem-solving activity it is own right. The problem is how…
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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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A quantitative PID tuning procedure is a step-by-step approach leading directly to a set of numerical values…
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This section does not describe a particular type of flowmeter, but rather a design that may be implemented for…
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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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