Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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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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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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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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Light is known to interact with matter in very specific ways, which may be exploited as a means of measuring…
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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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The efficient identification and correction of instrument calibration errors is an important function for…
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An electromechanical relay is an electrical switch actuated by an electromagnet coil. As switching devices,…
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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets 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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There are many process control applications in the industry where it is desirable to have multiple control…
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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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Most people reading this book have likely had the experience of adjusting water temperature using two hand…
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Electrical Resistance Resistance (\(R\)) is the dissipative opposition to an electric current, analogous to…
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The fundamental principle of electromagnetism is that an electric current will create a magnetic field at…
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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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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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The term “grid” refers to the conductors and equipment interconnecting power sources to power…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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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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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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In addition to Ohm’s Law, we have a set of rules describing how voltages, currents, and resistances…
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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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This section shows some of the many instrument symbols found in different types of technical diagrams used to…
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DC electric current signals may also be used to communicate process measurement information from transmitters…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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All substances are comprised of various elements in various combinations and proportions. Elements may thus be…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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Sensors used to measure vibration come in three basic types: displacement, velocity, and acceleration.…
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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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Converting between disparate units of measurement is the bane of many science students. The problem is worse…
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Learning how to tune PID controllers is a skill born of much practice. Regardless of how thoroughly you may…
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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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Many years ago, when I was first learning about electricity, I happened to discover a length of coaxial…
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One very convenient feature of waves is that their properties are universal. Waves of water in the ocean,…
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Many liquid substances undergo a process whereby their constituent molecules split into positively and…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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An variable-area flowmeter is one where the fluid must pass through a restriction whose area increases with…
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A form of protection against faults on long-distance power lines is called distance relaying, so named because…
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Take for instance the problem of measuring fluid flow through a pipe. To the layperson, this may seem to be a…
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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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There are many process control applications in the industry where it is desirable to have multiple control…
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