By definition, a source is a device delivering energy into a system, while a load is a device extracting…
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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 fundamental principle in instrumentation system troubleshooting is that every instrument has at least one…
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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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While the term “probability” may evoke images of imprecision, probability is in fact an exact…
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A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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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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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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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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Every programmable logic controller must have some means of receiving and interpreting signals from real-world…
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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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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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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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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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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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It is often useful to express the amplitude of an alternating quantity such as voltage or current in terms…
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Human-machine interfaces, or HMIs, are a critical part of nearly all control systems, complementing the…
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DC electric current signals may also be used to communicate process measurement information from transmitters…
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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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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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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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Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…
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In modern industry, the most popular form of field-level signal transmission for variable industrial…
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Most pneumatic instruments use a simple but highly sensitive mechanism for converting mechanical motion into…
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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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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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To show a practical process example, let’s examine three diagrams for a compressor 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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Learning PLC programming is a very important skill. If your job involves programming, then you will likely…
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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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I remember first learning about the world-wide Internet, and wondering what it actually looked like. The first…
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Perhaps the simplest form of solid or liquid level measurement is with a float: a device that rides on the…
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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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The final element of PID control is the “D” term, which stands for derivative. This is a calculus…
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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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Many traditional flowmeter technologies respond to the volumetric flow rate of the moving fluid.…
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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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“Feedforward” is a rather under-used control strategy capable of managing a great many types of…
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Weight-based level instruments sense process level in a vessel by directly measuring the weight of the vessel.…
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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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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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