The efficient identification and correction of instrument calibration errors is an important function for…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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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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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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The transformer is one of the most important components in all of AC circuitry. Principally used to…
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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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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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Imagine a major marathon race, where hundreds of runners gather in one place to compete. When the starting gun…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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 technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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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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While the term “probability” may evoke images of imprecision, probability is in fact an exact…
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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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Diagnostic ability is arguably the most difficult skill to develop within a student, and also the most…
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This section shows some of the many instrument symbols found in different types of technical diagrams used to…
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A proximity switch is one detecting the proximity (closeness) of some object. By definition, these switches…
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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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Valves can experience a number of problems, most of them either preventable or repairable. These problems can…
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Converting between disparate units of measurement is the bane of many science students. The problem is worse…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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All masses require force to accelerate (we can also think of this in terms of the mass generating a reaction…
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Like many other mathematical operations, the derivative and the integral perform inverse operations from each…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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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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Many traditional flowmeter technologies respond to the volumetric flow rate of the moving fluid.…
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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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An important design parameter of a control valve is the position it will “fail” to if it loses…
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An on/off valve is the fluid equivalent of an electrical switch: a device that either allows unimpeded flow or…
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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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Once while working as an instrument technician in an aluminum foundry, a mechanic asked me what it was that I…
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Using filter cells to eliminate wavelengths associated with interfering gases is called positive filtering in…
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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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As we have seen, the concept of integration is finding the accumulation of one variable multiplied by another…
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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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Labwork is an essential part of any science-based curriculum. Here, much improvement may be made over the…
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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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Like many other mathematical operations, the derivative and the integral perform inverse operations from each…
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A damper (otherwise known as a louvre) is a multi-element flow control device generally used to throttle large…
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The dispersion of visible light into its constituent colors goes all the way back to the 17th century with…
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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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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“As to methods there may be a million and then some, but principles are few. The man who grasps…
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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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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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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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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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When a high-energy photon strikes an atom, it may eject one of the lower-level electrons from its shell,…
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Capacitive level instruments measure electrical capacitance of a conductive rod inserted vertically into a…
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Steam boilers are very common in industry, principally because steam power is so useful. Common uses for steam…
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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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