Regarding HMI (Human Machine Interface) in automation:1.It allows operators to interact with the PLC and monitor machine status.2.HMIs are connected to PLCs using communication ports like Ethernet or RS-485.3.An HMI can only display text and cannot show graphical animations of processes.Which of the statements given above is/are correct?

Correct Answer: D - 1 and 2 only

Quick Concept Explanation

An HMI is the operator-facing interface to PLC/automation data. It can display graphical process mimic screens, trends, alarms, animations and controls, and commonly communicates over Ethernet or serial industrial links such as RS-485. Key relation: HMI reads/writes tags exposed by PLC/SCADA systems.

Exam focus: Use HMI for visualization and operator commands, not primary hardwired safety functions. Common trap: Modern HMIs are not text-only displays.

Statement-wise Verification

• Statement 1 - Correct.
  It allows operators to interact with the PLC and monitor machine status.
  HMI reads/writes tags exposed by PLC/SCADA systems.
• Statement 2 - Correct.
  HMIs are connected to PLCs using communication ports like Ethernet or RS-485.
  It can display graphical process mimic screens, trends, alarms, animations and controls, and commonly communicates over Ethernet or serial industrial links such as RS-485.
• Statement 3 - Incorrect.
  An HMI can only display text and cannot show graphical animations of processes.
  Modern HMIs provide graphics, trends, alarms and animated process mimic displays

Core Concept

An HMI is the operator-facing interface to PLC/automation data. It can display graphical process mimic screens, trends, alarms, animations and controls, and commonly communicates over Ethernet or serial industrial links such as RS-485.

Formula / Key Relationship

HMI reads/writes tags exposed by PLC/SCADA systems.

Why the Other Options Are Wrong

Option A is incorrect because it includes incorrect statement(s) 3. Option B is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 1. Option C is incorrect because it omits correct statement(s) 2.

Exam Shortcut / Approach

Use HMI for visualization and operator commands, not primary hardwired safety functions.

Common Mistake

Modern HMIs are not text-only displays.

Quick Revision

PLC-HMI Communication and Graphics is linked with Human Machine Interface, HMI and Industrial Automation. Use HMI for visualization and operator commands, not primary hardwired safety functions.