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Interview Questions related to Instrumentation and Automation


This post is based on my latest interview experience. In this post, you can find Interview Questions related to Instrumentation and Automation.

If you give the right answer to these questions, it will give you an unfair advantage in the interview.

so, I will provide how to give answers to it. Maybe in your next interview, these types of questions will be asked.

This question is not asked in every interview but in some cases, these types of questions are asked by the interviewer and then you will be stuck.

And this question is also based on my latest interview experience in a pharmaceutical company.

1. Full form of MES and ERP?

Ans: –

Manufacturing Execution System- MES

Enterprise Resource Planning- ERP

2. Full form of SIS?

Ans: –

Safety Instrument System – SIS

A safety instrument system is an added layer of protection for critical processes. where an extra layer of protection is needed if any functioning part fails.

I will write a post related to this topic in the future.

3. How will conductivity measure?

Ans: –

Conductivity is the inverse of resistivity so for measuring conductivity you have to find resistivity.

To find the resistivity of the medium you have to find resistance between two electrodes. and by using this equation you can find resistivity by knowing the resistance value

R= Resistivity * L / A

L/A = k (cell constant)

R = V / I

Conductivity = 1 / Resistivity

There are two methods of measuring conductivity.

4. Why is only 24 DC voltage used in the control cabinet?

Ans: –

There are multiple reasons

Safety: – 24 DC voltage is safely handled by humans without any injuries.

Standardize: – Most DC devices are operated on 24 DCV like Relay and Communication Card.

Size: – The size of 24VDC Equipment is less compared to AC equipment.

Heat: – The heating of circuits is less compared to higher voltage operating devices.

5. Why is a 20mA signal used in 4-20 mA standard signal?

Ans: –

if you know about almost all microcontrollers operating on a 5V DC signal. Due to the 250Ohm resistance in PLC input card voltage drop across register is become 5V when 20mA is passing in the loop.

And another reason is safety because the human heart can only stand up to 30mA current more than 30mA current leads to Heart failure.

6. What is the use of MES and ERP?

Ans: –

MES and ERP are the upper layers of industrial automation. MES and ERP operate on an enterprise level and transfer commands to the factory floor. To learn more about MES software please check out our post on MES software

MES: –

  • It is used for handling and planning production
  • collect real-time process data from the SCADA system
  • Reduce paperwork
  • MES helps the entire project lifecycle for less downtime and maintenance time.
  • production planning and material handling and tracking

ERP: –

  • It is used for material management
  • It is also helping with planning human resources management
  • Material purchase and selling
  • Bill of material

Ans: –

MES: –

  • Emerson
  • PLEX
  • IQMS

ERP: –

  • SAP
  • SAGE
  • Microsoft Dynamics

8. Which standards are followed for plant functional safety?

Ans: –

IEC 61508

IEC 61511

These are the standards followed in plant functional safety. I am thinking about writing a post related to plant functional safety so stay tuned.

9. Create logic gates using Ladder Logic programming

10. Create a square Wave generator using ladder logic

EndNote: –

So, this is my interview question series and I will try to add more and more questions whenever I get back, I will categorize interview questions topic-wise so you can easily find and prepare.

And if you want to share your interview experience and question then please comment below.

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KISHAN MENDAPARAhttps://worldofinstrumentation.com
Instrumentation and Control Engineer


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