“Polyphase” means “many phases,” describing a form of AC electrical system where…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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One of the great benefits of digital technology is the ability to communicate vast amounts of information over…
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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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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Many years ago, when I was first learning about electricity, I happened to discover a length of coaxial…
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Another category of control strategies involves the use of signal relays or function blocks with the ability…
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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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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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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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Regardless of valve type, all stem-actuated control valves require some form of seal allowing motion of the…
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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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Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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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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Suppose we wished to measure the rate of propane gas flow through a hose to a torch: Flowmeters appropriate…
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An interesting parallel to the “unity fraction” unit conversion technique is something referred to…
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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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Stoichiometry is the accounting of atoms before and after a chemical reaction. It is an expression of the Law…
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Another category of control strategies involves the use of signal relays or function blocks with the ability…
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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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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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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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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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Earlier in this chapter you were shown a model of a nitrogen atom with a dense nucleus (comprised of protons…
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The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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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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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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 laser is a light source emitting waves of light that not only share the exact same frequency (color)…
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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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As we have seen, the concept of differentiation is finding the rate-of-change of one variable compared to…
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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…
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The following collection of photographs chronicles the complete disassembly of a Fisher E-body globe valve…
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Much of our knowledge about atomic structure comes from experimental data relating the interaction between…
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These fortifications focus on human behavior rather than system design or component selection. In some ways…
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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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Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…
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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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The following animation shows a rotating phasor in three-dimensional form. The phasor rotates in a complex…
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This section does not describe a particular type of flowmeter, but rather a design that may be implemented for…
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The key to understanding how three-phase electric motors work is to have an accurate mental picture of the…
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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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A unique form of differential pressure-based flow measurement deserves its own section in this flow…
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Most pneumatic instruments use a simple but highly sensitive mechanism for converting mechanical motion into…
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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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Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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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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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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