A fundamental principle in instrumentation system troubleshooting is that every instrument has at least one…
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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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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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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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The efficient identification and correction of instrument calibration errors is an important function for…
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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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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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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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A form of protection against faults on long-distance power lines is called distance relaying, so named because…
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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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Any power grid large enough to meet the demand of an entire nation must have multiple generators drawing from…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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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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In a manually-controlled process, a human operator directly actuates some form of final control element…
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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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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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The fundamental principle of electromagnetism is that an electric current will create a magnetic field at…
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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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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 reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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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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Linearity of Measurement Instruments The purpose of calibration is to ensure the input and output of an…
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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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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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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 completely different way of measuring liquid level in vessels is to bounce a traveling wave off the surface…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Some self-powered (4-wire) analog electronic transmitters are designed to behave as electrical loads rather…
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A positive displacement flowmeter is a cyclic mechanism built to pass a fixed volume of fluid through with…
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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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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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Area refers to the size of two-dimensional surface. Volume refers to the size of a three-dimensional space. To…
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A chemical reaction resulting in a net release of energy is called exothermic. Conversely, a chemical reaction…
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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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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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Mechanical pressure-sensing elements include the bellows, the diaphragm, and the bourdon tube. Each of these…
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A unique form of differential pressure-based flow measurement deserves its own section in this flow…
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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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In order to provide an interface between the internal (digital) world of a computer and the external (analog)…
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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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A unique form of technical diagram for describing the abstract functions comprising a control system (e.g. PID…
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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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