One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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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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Perhaps the most confusing aspect of discrete sensors is the definition of a sensor’s normal status.…
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A fundamental principle in instrumentation system troubleshooting is that every instrument has at least one…
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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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When control valves operate between fully open and fully shut, they serve much the same purpose in process…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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An important design parameter of a control valve is the position it will “fail” to if it loses…
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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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The advent of “smart” field instruments containing microprocessors has been a great advance for…
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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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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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Current is the name we give to the motion of electric charges from a point of high potential to a point of low…
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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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Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…
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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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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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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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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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A proximity switch is one detecting the proximity (closeness) of some object. By definition, these switches…
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The following photograph shows a large air blower in a wastewater treatment facility equipped with a…
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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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Fieldbus devices require far more attention in their initial setup and commissioning than their analog…
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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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A temperature switch is one detecting the temperature of some substance. Temperature switches often use…
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Measuring the flow rate of liquid through an open channel is not unlike measuring the flow rate of a liquid…
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In reliability engineering, it is important to be able to quantity the reliability (or conversely, the…
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Several different technologies exist for the conversion of fluid pressure into an electrical signal response.…
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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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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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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A laser is a light source emitting waves of light that not only share the exact same frequency (color)…
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While the term “probability” may evoke images of imprecision, probability is in fact an exact…
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To show a practical process example, let’s examine three diagrams for a compressor control system,…
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At the root of successful system diagnosis is a rigorous adherence to scientific reasoning. There exists no…
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As a general rule, high achievement only takes place in an atmosphere of high expectations. Sometimes these…
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“Polyphase” means “many phases,” describing a form of AC electrical system where…
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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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Using filter cells to eliminate wavelengths associated with interfering gases is called positive filtering in…
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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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In some process applications, it is important that the control valve be able to completely stop fluid flow…
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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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A fundamental limitation of proportional control has to do with its response to changes in setpoint and…
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Electrical power grids primarily consist of three-phase AC circuits. This means most power lines (transmission…
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Most pneumatic instruments use a simple but highly sensitive mechanism for converting mechanical motion into…
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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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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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The following photograph shows a large air blower in a wastewater treatment facility equipped with a…
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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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Suppose we wished to measure the rate of propane gas flow through a hose to a torch: Flowmeters appropriate…
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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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As a general rule, high achievement only takes place in an atmosphere of high expectations. Sometimes these…
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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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Learning is not merely a process of information transfer. It is first and foremost a transformation of…
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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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The vast majority of modern process transmitters (both analog and digital) come equipped with a feature known…
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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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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