30 PLC engineer interview questions, all based on the experience summary of senior electrical engineers!

Detail

This question tests the basic understanding of a PLC's functionality. An ideal answer should cover the definition of a Programmable Logic Controller (PLC) and its role in industrial automation, including how it executes a series of user-programmed instructions to control machinery or processes.

The answer should include the CPU, power supply, I/O modules, and communication interfaces. Additional points might cover the use of human-machine interfaces (HMIs), sensors, and actuators in a PLC system.

Candidates should discuss programming languages like Ladder Logic, Function Block Diagram (FBD), or Structured Text (ST), and also touch on simulation software and testing methodologies such as unit testing and system integration testing.

Responses should include locking out and tagging out procedures, proper use of personal protective equipment (PPE), and adherence to electrical codes and standards.

Look for a systematic methodology that includes checking power supplies, input/output status, and communication systems, as well as using diagnostic tools and software.

The candidate should highlight the versatility, reprogrammability, and advanced functionalities of PLCs as opposed to the fixed, physical wiring of relay logic systems.

Prospects should talk about their practical experience in designing or using HMIs and the methods used to connect an HMI to a PLC, such as through industrial communication protocols.