Why text-based OI has its place on the machine

Simple message display and operator input device doesn’t need microprocessor for data manipulation.

HMI GUI

Technically, an operator interface (OI) and a human-machine interface (HMI) could be considered the same thing, and the differences between them are becoming increasingly blurred. The generally accepted definition of an OI is a usually a text-based display that may have a limited number of buttons to allow operator input to the control device. Some alpha-numeric displays have a number of programmable function keys and a full keyboard, but these are becoming rare because of the continuously falling prices of graphical touchscreen interfaces. An HMI is a usually a graphic-based display that provides a greater number of operator input options. One often-cited way to…

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How to tune PID loops

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Voices: Real Answers

How to decide between PNP and NPN

What signal level sensors and I/O modules should you standardize on?

By Mike Bacidore, editor in chief

A Control Design reader writes: My question arises due to machines we received at our manufacturing plant in Arizona from an OEM in Asia. All of the PLC 24 Vdc digital input modules were NPN (sourcing 24 V dc) and our plant’s standard is PNP inputs (sinking 24 Vdc inputs). These signal levels…

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  • Why text-based OI has its place on the machine

    By Tom Stevic, contributing editor

    Technically, an operator interface (OI) and a human-machine interface (HMI) could be considered the same thing, and the differences between them are becoming increasingly blurred. The generally accepted definition of an OI is a usually a text-based display that may have a limited number of buttons…

    Full Story

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