A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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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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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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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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The following photograph shows a large air blower in a wastewater treatment facility equipped with a…
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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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In order to provide an interface between the internal (digital) world of a computer and the external (analog)…
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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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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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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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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PID control can be a confusing concept to understand. Here, a brief summary of each term within PID (P. I, and…
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Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…
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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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An exciting development in industrial instrumentation is the WirelessHART radio communication standard,…
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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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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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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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A very common form of on/off valve used for pneumatic and hydraulic systems alike is the solenoid valve. A…
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A hand switch is exactly what the name implies: an electrical switch actuated by a person’s hand motion.…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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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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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose…
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Modern analog-to-digital converters are phenomenally accurate, dependable, repeatable, and surprisingly…
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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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Sensors used to measure vibration come in three basic types: displacement, velocity, and acceleration.…
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One of the simplest classes of temperature sensor is one where temperature effects a change in electrical…
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Layer 1 of the OSI Reference Model is where we define the “physical” elements of a digital data…
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Binary patterns are not just able to represent numerical values. Given a standardized code, they may represent…
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In contrast to quantitative tuning procedures where definite numerical values for P, I, and D controller…
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Solids tend to expand when heated. The amount that a solid sample will expand with increased temperature…
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In November of 2007 a new computer virus was submitted to a virus scanning service. The purpose of this new…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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DC electric current signals may also be used to communicate process measurement information from transmitters…
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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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Suppose we wished to measure the consumption of propane over time for a large propane storage tank supplying a…
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