Importance of HMI

In control rooms of old, the number of alarms was limited by the amount of space

on the control room panel board and the cost of wiring equipment from the production area to the board.

Annunciators, indicators and switches (to acknowledge and clear a resolved alarm)

had to be essential to justify a place on the panel.

If a new alarm was needed, an existing alarm would usually have to  make way.

This began to change with digital signals and the distributed control system (DCS) in the 1980s.

Panel boards were replaced by monitors and servers,

and signals were transmitted from plant equipment to computer processors,

where the signals were turned into actionable information.

But the alarms were overloading the control room and terms such as flooding,

nuisance, chattering, fleeting and stale were coined to describe them and their effect on the operators.

The modern HMIs are equipped with high performance grayscale graphics,

using color carefully and provide effective alarm handling and analysis.