The vast majority of modern process transmitters (both analog and digital) come equipped with a feature known…
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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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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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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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Level gauges are perhaps the simplest indicating instrument for liquid level in a vessel. They are often found…
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At the next OSI Reference Model layer (layer 4) is a set of protocols specifying how reliable communication…
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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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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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When control valves operate between fully open and fully shut, they serve much the same purpose in process…
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A powerful mathematical concept useful for analyzing practically any physical system – electrical…
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Every flow-measuring instrument exploits a physical principle to measure the flow rate of fluid stream.…
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Flow, by definition, is the passage of material from one location to another over time. So far this chapter…
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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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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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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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In November of 2007 a new computer virus was submitted to a virus scanning service. The purpose of this new…
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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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At the root of successful system diagnosis is a rigorous adherence to scientific reasoning. There exists no…
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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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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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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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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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A pressure switch is one that detects the presence of fluid pressure. Pressure switches often use diaphragms…
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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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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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An important design parameter of a control valve is the position it will “fail” to if it loses…
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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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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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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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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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“Radio” systems use electromagnetic fields to communicate information over long distances through…
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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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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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In our first signal characterization example, we tackle the problem of measuring fluid flow through a pipe. To…
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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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Temperature measurement devices may be classified into two broad types: contact and non-contact. Contact-type…
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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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A completely different way of measuring liquid level in vessels is to bounce a traveling wave off the surface…
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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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A great many precision instruments use the principle of balance to measure some quantity. Perhaps the simplest…
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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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Data-processing modules within FF systems are known as function blocks. Sometimes these blocks serve merely to…
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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 pressure switch is one that detects the presence of fluid pressure. Pressure switches often use diaphragms…
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As we have seen, the concept of integration is finding the accumulation of one variable multiplied by another…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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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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A positive displacement flowmeter is a cyclic mechanism built to pass a fixed volume of fluid through with…
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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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In some process applications, it is important that the control valve be able to completely stop fluid flow…
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The electrical conductivity of liquids is an important analytical measurement in many industrial processes.…
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Learning PLC programming is a very important skill. If your job involves programming, then you will likely…
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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 proximity switch is one detecting the proximity (closeness) of some object. By definition, these switches…
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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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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Temperature measurement devices may be classified into two broad types: contact and non-contact. Contact-type…
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