As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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A wise PLC programmer once told me that the first thing any aspiring programmer should learn about the PLC…
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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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Some analyzers measure the composition of a process stream by directly immersing the sensing element in that…
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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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Much of our knowledge about atomic structure comes from experimental data relating the interaction between…
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In a manually-controlled process, a human operator directly actuates some form of final control element…
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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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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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A temperature switch is one detecting the temperature of some substance. Temperature switches often use…
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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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In order for any PID controller to be practical, it must be able to do more than just implement the PID…
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Self-balancing pneumatic instrument mechanisms are very similar to negative-feedback operational amplifier…
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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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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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Many years ago, when I was first learning about electricity, I happened to discover a length of coaxial…
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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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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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The fundamental principle of electromagnetism is that an electric current will create a magnetic field at…
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The Law of Mass Conservation states that matter can neither be created nor destroyed. The Law of Energy…
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Much has been written about the benefits of robust PID control. Increased productivity, decreased equipment…
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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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A limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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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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In order to provide an interface between the internal (digital) world of a computer and the external (analog)…
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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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Sometimes we encounter a diversity of instrument signal standards in one control system. Such is the case with…
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DC electric current signals may also be used to communicate process measurement information from transmitters…
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Thermodynamics is the study of heat, temperature, and their related effects in physical systems. As a subject,…
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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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A great many precision instruments use the principle of balance to measure some quantity. Perhaps the simplest…
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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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float directly sets…
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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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Modern analog-to-digital converters are phenomenally accurate, dependable, repeatable, and surprisingly…
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There is much to be said for neatness of assembly in electrical signal wiring. Even though the electrons…
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As we have seen, feedforward control is a way to improve the stability of a feedback control system in the…
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A different strategy for controlling the flow of fluid is to insert a rotary element into the flow path.…
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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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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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The following animation shows how a radio-energy pulse travels down and then up the waveguide of a guided-wave…
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The majority of flowmeter technologies operate on the principle of interpreting fluid flow based on the…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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The next level of detail is the Process and Instrument Diagram, or P&ID. Here, we see a “zooming…
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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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Like many other mathematical operations, the derivative and the integral perform inverse operations from each…
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A very simple device used to measure pressure is the manometer: a fluid-filled tube where an applied gas…
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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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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust 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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The following photograph shows a large air blower in a wastewater treatment facility equipped with a…
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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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Fluid pressure exerts force on any surface area it contacts, as described by the formula \(F = PA\). One…
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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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The following collection of photographs chronicles the complete disassembly of a Fisher E-body globe valve…
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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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Binary patterns are not just able to represent numerical values. Given a standardized code, they may represent…
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