Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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The final step in treating wastewater before releasing it into the natural environment is to kill any harmful…
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The three “elementary” particles of matter comprising all atoms are electrons, protons, and…
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Most of these formulae appear in molecular chemical form rather than structural form. For example, ethanol…
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A chemical reaction resulting in a net release of energy is called exothermic. Conversely, a chemical reaction…
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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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As we have seen, feedforward control is a way to improve the stability of a feedback control system in the…
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A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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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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A great many chemical composition measurements may be made indirectly by means of electricity, if those…
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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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As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…
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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 pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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“Radio” systems use electromagnetic fields to communicate information over long distances through…
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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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DC electric current signals may also be used to communicate process measurement information from transmitters…
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To show a practical process example, let’s examine three diagrams for a compressor control system,…
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In November of 2007 a new computer virus was submitted to a virus scanning service. The purpose of this new…
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An important performance parameter for transmitter instruments is something often referred to as turndown or…
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A unique form of technical diagram for describing the abstract functions comprising a control system (e.g. PID…
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Control valves are supposed to deliver reliable, repeatable control of process fluid flow rate over a wide…
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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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A control strategy similar to ratio control is relation control. This is similar to ratio control in that a…
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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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Cyber-security seems to have its own vocabulary, ranging from unwieldy technical acronyms to slang terms…
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Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose…
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The two “process variables” we rely on most heavily in the field of electrical measurement and…
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Sample sizes of chemical substances are often measured in moles. One mole of a substance is defined as a…
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Electromechanical relays may be connected together to perform logic and control functions, acting as logic…
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Most of these formulae appear in molecular chemical form rather than structural form. For example, ethanol…
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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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In this section I will show screenshots from a process loop simulation program illustrating the effectiveness…
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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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Calculus has a reputation for being difficult to learn, and with good reason. The traditional approach to…
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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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The dispersion of visible light into its constituent colors goes all the way back to the 17th century with…
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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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Suppose we wished to measure the rate of propane gas flow through a hose to a torch: Flowmeters appropriate…
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A flow switch is one detecting the flow of some fluid through a pipe. Flow switches often use…
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A number of different sensors used in instrumentation generate DC voltage signals proportional to the process…
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A very common form of on/off valve used for pneumatic and hydraulic systems alike is the solenoid valve. A…
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An engineer named Bob Metcalfe conceived the idea of Ethernet in 1973, while working for the Xerox research…
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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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Perhaps the most important rule to obey when using pneumatic instruments is to maintain clean and dry…
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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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A chemical reaction resulting in a net release of energy is called exothermic. Conversely, a chemical reaction…
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These fortifications focus on human behavior rather than system design or component selection. In some ways…
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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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