A laser is a light source emitting waves of light that not only share the exact same frequency (color)…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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Modern analog-to-digital converters are phenomenally accurate, dependable, repeatable, and surprisingly…
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Any conductor possesses a characteristic called inductance: the ability to store energy in the form of a…
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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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A flow switch is one that detects the flow of some fluid through a pipe. Flow switches often use…
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Capacitive level instruments measure electrical capacitance of a conductive rod inserted vertically into a…
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Some problem-solving techniques are unique to quantitative problems, involving mathematical calculations. In…
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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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Learning is not merely a process of information transfer. It is first and foremost a transformation of…
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To show a practical process example, let’s examine three diagrams for a compressor control system,…
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Displacer level instruments exploit Archimedes’ Principle to detect liquid level by continuously…
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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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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…
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I remember first learning about the world-wide Internet, and wondering what it actually looked like. The first…
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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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When a high-energy photon strikes an atom, it may eject one of the lower-level electrons from its shell,…
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The efficient identification and correction of instrument calibration errors is an important function for…
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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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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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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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It is often useful to express the amplitude of an alternating quantity such as voltage or current in terms…
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Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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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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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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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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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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A completely different way of measuring liquid level in vessels is to bounce a traveling wave off the surface…
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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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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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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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Every flow-measuring instrument exploits a physical principle to measure the flow rate of fluid stream.…
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Although analog electronic process controllers are considered a newer technology than pneumatic process…
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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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DC electric current signals may also be used to communicate process measurement information from transmitters…
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Perhaps the most important rule to obey when using pneumatic instruments is to maintain clean and dry…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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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In reliability engineering, it is important to be able to quantity the reliability (or conversely, the…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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The three “elementary” particles of matter comprising all atoms are electrons, protons, and…
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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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Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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An important legacy technology for all kinds of continuous measurement is the self-balancing system. A…
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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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The majority of flowmeter technologies operate on the principle of interpreting fluid flow based on the…
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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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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A limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…
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Electrical power grids primarily consist of three-phase AC circuits. This means most power lines (transmission…
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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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The following animation shows a rotating phasor in three-dimensional form. The phasor rotates in a complex…
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