Digital Representation of Numerical Data

Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…

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4-wire “Passive” Versus “Active” Output Transmitters

Some self-powered (4-wire) analog electronic transmitters are designed to behave as electrical loads rather…

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Material Volume Measurement

A variety of technologies exist to measure the quantity of stored material in a vessel. For liquid…

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Heuristic PID Tuning Procedures

In contrast to quantitative tuning procedures where definite numerical values for P, I, and D controller…

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Transmitter Damping Adjustments

The vast majority of modern process transmitters (both analog and digital) come equipped with a feature known…

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Zero and Span Adjustments (Analog Instruments)

Linearity of Measurement Instruments The purpose of calibration is to ensure the input and output of an…

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Equivalent Series and Parallel Circuits

Impedance in a series circuit is the orthogonal sum of resistance and reactance: \[Z = \sqrt{R^2 + (X_L -…

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On/off Control (Bang-bang Control)

Once while working as an instrument technician in an aluminum foundry, a mechanic asked me what it was that I…

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Teaching Technical Theory

Learning is not merely a process of information transfer. It is first and foremost a transformation of…

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Relating 4 to 20 mA Signals to Instrument Variables

A 4 to 20 mA current signal represents some signal along a 0 to 100 percent scale. Usually, this scale is…

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Metric Prefixes and Prefix Scale

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Atomic Theory and Chemical Symbols

The three “elementary” particles of matter comprising all atoms are electrons, protons, and…

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Limit Switches

A limit switch detects the physical motion of an object by direct contact with that object. An example of a…

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Flow Measurement in Open Channels

Measuring the flow rate of liquid through an open channel is not unlike measuring the flow rate of a liquid…

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Basic Components Common to all Radio Systems

“Radio” systems use electromagnetic fields to communicate information over long distances through…

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A Comparison of PID Controller Tuning Techniques

In this section I will show screenshots from a process loop simulation program illustrating the effectiveness…

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National Institute of Standards and Technology (NIST) Traceability

As defined previously, calibration means the comparison and adjustment (if necessary) of an instrument’s…

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Introduction to Calculus

Calculus. Few areas of mathematics are as powerfully useful in describing and analyzing the physical…

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Classified Areas and Electrical Safety Measures

Any physical location in an industrial facility harboring the potential of explosion due to the presence of…

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DC Motor Speed Control

DC electric motors generate torque by a reaction between two magnetic fields: one field established by…

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Overpressure Protection Devices

Fluid pressure exerts force on any surface area it contacts, as described by the formula \(F = PA\). One…

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