plc job interview questions

Do you want to test your PLC knowledge, practice for a PLC job, or just learn more about PLC?

Based on my experience working in the PLC domain, I am compiling a list of PLC interview questions and answers.

Whether you are a novice or an expert, this list of interview questions will improve your understanding of PLCs.

Top 10 Frequently Asked PLC Interview Questions
  • Explain PLC?
  • What are the different parts of automation?
  • What are the implementations of PLC automation?
  • Role of PLC in Automation?
  • What is redundancy in PLC?
  • What is scan in PLC?
  • How does a Latch coil work?
  • What is a draw close to the control relay?


Common PLC Interview Questions And Sample Answers

Here are some typical PLC interview questions and sample responses:

How do you determine the memory size for a PLC installation?

This inquiry enables the interviewer to learn more about your capacity for making decisions. They can judge how you use your knowledge to make important project decisions thanks to it. You can describe your working style and decision-making process in response to this kind of question.

“In my previous projects, I assessed five crucial factors to determine the PLC memory size, including the size of the control program, the quantity of input and output points, the needs for data collection, the supervisory functions, and the potential for future expansion. I obtained the values for these variables from the relevant teams, after which I chose the PLC memory size that met all criteria. “.

Consider a burglar alarm that activates if a window or motion sensor detects an unauthorised person. Can you identify the inputs and outputs for this system in PLC programming?

These types of inquiries may be used by the interviewer to gauge your proficiency with coding. The interview may also include a formal coding test to determine how well you comprehend the fundamentals of PLC programming and how you apply them. Along with writing the code, you can also describe your decision-making process.

Example: “Basically, there are two sensors in this system. When it detects an unauthorized person, the motion detector’s output turns true. In the window sensor, the default output is always true. The circuit snaps, the current stops flowing, and the outputs’ status changes to false when someone tries to break the window. The master switch, motion sensor, window sensor, deactivate switch, and button to stop the alarm are on the list of this system’s inputs. Its outputs are the master coil, alarm, and alarm coil. “.

What is the role of PLC in automation?

PLC plays most important role in automation. PLCs carry out all monitoring and controlling operations.

PLC processes logic via CPU and memory, senses input through I/P modules, and outputs through output modules.

Within a very short moment, it conducts accurate activities. That is one of the factors for the widespread use of PLC in the industrial sector today.

Looking to work in the manufacturing industry, want to work as a PLC technician, or want to move up into a more senior technical role? Whether you are a new or veteran PLC technician, it’s important to prepare for your interview. While there are many steps to ensure you are ready once you get to the interview, this blog will focus on preparing for common technical questions.

Even though you ought to be able to respond to these technical inquiries, your prospective employer will also want to get to know you. Be prepared to discuss how you resolved a workplace conflict, the steps you took to reach a critical decision at work, or what motivates you to do your best work. When deciding whether to hire a candidate, finding one who is a good corporate fit could be just as crucial as ensuring they have the necessary skills.

It’s crucial to prepare for interviews if you want to get a job. You must not only do your homework and research the company, but you must also be prepared to answer difficult interview questions. Planning ahead will help you feel more at ease and confident, which will improve your interview performance and increase your chances of landing the job.

What are the types of PLC programming languages?

There are five different categories of PLC programming languages based on IEC-61131-3 International Standards, including:


What is PLC short answer?

An industrial computer control system called a PROGRAMMABLE LOGIC CONTROLLER (PLC) continuously monitors the state of input devices and decides how to control the state of output devices based on a unique program.

What are the 5 PLC programming languages?

The five PLC programming languages defined in the IEC’s standard are:
  • Ladder Logic.
  • Function Block Diagram.
  • Sequential Function Charts.
  • Structured Text.
  • Instruction List.

What is basic PLC knowledge?

Basic PLC operations A CPU (central processing unit) and input and output points or modules make up a PLC. Inputs work to transform a variety of analog and digital signals from various sensors and field devices into logic signals that are compatible with CPUs.

How a PLC works step by step?

Step-By-Step Procedure for Programming PLC Using Ladder Logic
  1. Step 1: Analyze and Get the Idea of Control Application.
  2. Step 2: Create a flowchart and list all the conditions to determine the design.
  3. Step3: Open and Configure the PLC Programming Software. …
  4. Step 4: Add the Required Rungs and Address Them.

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