Human-Machine Interface (HMI) in SCADA: 

• Human-Machine Interface abbreviated as HMI is a user interface that is a combination of hardware and software that permits easy interaction between human and machine.
• The main purpose of establishing such an interaction between humans and machines is to control and monitor the processes ongoing at remote locations without physically being present at that particular location.
• Its major aim is to ensure effective operation through controlling the system which is being monitored.
• This is done by a human operator that takes the operational decisions and holds the power for manual overriding of automatic control operation in case of emergency.

Functions of HMI:

1. Visualizing data display.
2. Monitoring the inputs and outputs of the machines.
3. Tracking of production time, trends, etc.
4. Performing the required changes when needed.
    

Components of Human-Machine Interface: 

1. Operator Console:

• The operator console is a very important part of HMI as it has various units like visual display units (VDUs), pointer/cursor, keyboard, and communication facilities, etc.
• The VSUs are basically monitoring screens like CRT, LED, LCD, etc. with antiglare screen coating.
• The work of cursor is performed by mouse, trackball, or the touch-screen facility. All the monitors share a keyboard and cursor which moves through all the screens without user intervention.
• In SCADA systems, a single operator handles around 3 to 4 monitors so as to have a display facility with full graphics that facilitates proper planning and monitoring of the system.
• Audible alarms are also present at the operator console that intimates the operator regarding the event occurring in the system and also informs the user whenever there is a need to change the existing event.
   

2. Operator Dialogue:

• Dialogue boxes act as a communication bridge between the operator and the computer.
• It pops up whenever there is any information to be given or in case of any query while operating.
• The engineer must design it in the easiest possible way so that its commands are simple and easily understandable.
• The function keys present in the keyboard are programmed so that any major changes do not require much of the operator’s efforts.
   

3. Mimic Diagram:

• In the large station centre, a mimic diagram is a crucial component through which the operator gets the full view of the processes under control.
• This needs large multiple screen displays like LCDs or LEDs with SCADA operability.
• There is a mosaic map board either of static or dynamic nature which is directly linked to HMI.
• So, this offers upgrades of the map board directly at the time when HMIs are upgraded.

4. Peripheral devices:

• The peripheral devices used in interconnection with HMIs are printers.
• Majorly these are of 3 types, one is used to print the alarms and SOEs.
• A colour printer is used to capture screenshots.
• While the third one is a laser printer which is black and white and prints the latest reports.