The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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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 reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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PID control can be a confusing concept to understand. Here, a brief summary of each term within PID (P. I, and…
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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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Recall that an exothermic chemical reaction is one that releases a net sum of energy, as opposed to an…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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To summarize some of the key points and concepts for teaching: Do not waste class time transmitting facts to…
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Any power grid large enough to meet the demand of an entire nation must have multiple generators drawing from…
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At the next OSI Reference Model layer (layer 4) is a set of protocols specifying how reliable communication…
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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 very common method for directly controlling low flow rates of fluids is to use a device known as a metering…
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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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The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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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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An exciting development in industrial instrumentation is the WirelessHART radio communication standard,…
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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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One very convenient feature of waves is that their properties are universal. Waves of water in the ocean,…
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Up until this point, we have explored various types of instrumentation diagram, each one making reference to…
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Certain types of nuclear radiation easily penetrates the walls of industrial vessels, but is attenuated by…
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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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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 quantitative PID tuning procedure is a step-by-step approach leading directly to a set of numerical values…
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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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In this section I will show screenshots from a process loop simulation program illustrating the effectiveness…
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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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As we have seen, the concept of differentiation is finding the rate-of-change of one variable compared to…
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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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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…
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A technological advance introduced in the late 1980’s was HART, an acronym standing for Highway…
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A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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An interesting parallel to the “unity fraction” unit conversion technique is something referred to…
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The following photograph shows a large air blower in a wastewater treatment facility equipped with a…
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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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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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RTDs are completely passive sensing elements, requiring the application of an externally-sourced electric…
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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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The following animation shows a rotating phasor in three-dimensional form. The phasor rotates in a complex…
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