Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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In modern industry, the most popular form of field-level signal transmission for variable industrial…
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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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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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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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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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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 limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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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 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 confusing aspect of discrete sensors is the definition of a sensor’s normal status.…
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The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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DC electric current signals may also be used to communicate process measurement information from transmitters…
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Much of our knowledge about atomic structure comes from experimental data relating the interaction between…
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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…
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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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float directly sets…
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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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Finally, we arrive at the loop diagram (sometimes called a loop sheet) for the compressor surge control system…
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A level switch is one detecting the level of liquid or solid (granules or powder) in a vessel. Level switches…
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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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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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Much has been written about the benefits of robust PID control. Increased productivity, decreased equipment…
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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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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The concepts of calibration (trimming) and ranging are often difficult for new students of instrumentation to…
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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 variety of technologies exist to measure the quantity of stored material in a vessel. For liquid…
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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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Many liquid substances undergo a process whereby their constituent molecules split into positively and…
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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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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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A much simpler alternative to continuous vibration sensors (displacement or acceleration) and monitoring…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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A powerful mathematical concept useful for analyzing practically any physical system – electrical…
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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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Hydrogen ion activity in aqueous (water-solvent) solutions is a very important parameter for a wide variety of…
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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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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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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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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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The vast majority of modern process transmitters (both analog and digital) come equipped with a feature known…
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Once while working as an instrument technician in an aluminum foundry, a mechanic asked me what it was that I…
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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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The Law of Continuity for fluids states that the product of mass density (\(\rho\)), cross-sectional pipe area…
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It is possible to convey electrical power and communicate analog information over the same two wires using 4…
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There are many process control applications in the industry where it is desirable to have multiple control…
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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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Stoichiometry is the accounting of atoms before and after a chemical reaction. It is an expression of the Law…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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Temperature measurement devices may be classified into two broad types: contact and non-contact. Contact-type…
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A much simpler alternative to continuous vibration sensors (displacement or acceleration) and monitoring…
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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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In this section I will show screenshots from a process loop simulation program illustrating the effectiveness…
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