Process and Instrument Diagrams

The next level of detail is the Process and Instrument Diagram, or P&ID. Here, we see a “zooming…

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Differential Pressure Transmitters

One of the most common, and most useful, pressure measuring instruments in industry is the differential…

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Relation Control

A control strategy similar to ratio control is relation control. This is similar to ratio control in that a…

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4 to 20 mA Analog Current Signals

In modern industry, the most popular form of field-level signal transmission for variable industrial…

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Pneumatic Sensing Elements

Most pneumatic instruments use a simple but highly sensitive mechanism for converting mechanical motion into…

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ANSI/IEEE Function Number Codes

In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…

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Ultrasonic (Sound) Echo Level Measurement

A completely different way of measuring liquid level in vessels is to bounce a traveling wave off the surface…

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Metric Prefixes and Prefix Scale

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Limit, Selector, and Override Controls

Another category of control strategies involves the use of signal relays or function blocks with the ability…

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Temperature Sensor Accessories

One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as…

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Examples of PLC Systems

Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…

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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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Introduction to Protective Relaying

Circuit breakers used in residential, commercial, and light industrial service are self-tripping devices: they…

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Control Valve Sizing

When control valves operate between fully open and fully shut, they serve much the same purpose in process…

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Legal Code

Creative Commons Attribution 4.0 International Public License By exercising the Licensed Rights (defined…

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Wastewater Disinfection Example

The final step in treating wastewater before releasing it into the natural environment is to kill any harmful…

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VSD and VFD Motor Drive Features

Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…

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Self-regulating, Integrating, and Runaway Process Characteristics

Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…

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Weighfeeders

A special type flowmeter suited for powdered or granular solids is the weighfeeder. One of the most common…

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Solenoid Valves

A very common form of on/off valve used for pneumatic and hydraulic systems alike is the solenoid valve. A…

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