75 Instrumentation Interview Questions (With Sample Answers)

By Indeed Editorial Team

Published 3 September 2022

The Indeed Editorial Team comprises a diverse and talented team of writers, researchers and subject matter experts equipped with Indeed's data and insights to deliver useful tips to help guide your career journey.

Instrumentation engineers and professionals seeking jobs in fields like electrical engineering, robotics or electrical design are most likely to encounter process control and instrumentation questions in their interview. These questions are common in industries like steel, chemical and power production, frequently asked by multinational and national oil and gas, paper, fertiliser and pharmaceutical companies. Knowing the kinds of questions, you may encounter can help you prepare suitable answers and feel more confident in your ability to impress the hiring manager.

In this article, we discuss 75 general, in-depth and experience-based instrumentation interview questions, along with some sample answers for your reference, and also explain why employers ask them.

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General Instrumentation Interview Questions

Here are 10 general instrumentation interview questions the interviewer might ask you to better understand your motivation for pursuing this career path and test your basic knowledge of instrumentation:

  1. What motivated you to become an instrumentation engineer?

  2. What do you understand by instrumentation? Where is it useful?

  3. What are your favourite process control and instrumentation tools?

  4. How do you stay updated on industry developments?

  5. What are some important qualities for instrumentation engineers?

  6. What aspects of this job do you find most challenging? How do you overcome these challenges in your work?

  7. Tell me about some of your greatest strengths and weaknesses.

  8. Why do you want to work with our organisation?

  9. What are your salary expectations?

  10. Why do we hire you?

Related: How To Prepare For A Job Interview

Questions About Experience And Background

Here are 10 career-specific questions you may encounter when the interviewer is curious about specific details in your work history and educational qualifications:

  1. Tell me about your background in instrumentation engineering.

  2. What are your professional qualifications? Do you have any training or certifications?

  3. Outline your practical/industry-specific experience in using instrumentation.

  4. How would your past employers describe you?

  5. What were your responsibilities in your previous position?

  6. Which technologies do you have experience using in your past roles?

  7. Share an example of a time you successfully used instrumentation principles to develop a new device or process.

  8. How do you use instrumentation to redesign older devices employed to control electronic or mechanical systems?

  9. What are some of your proficiencies that can be an asset to the company and this position?

  10. Which aspects of this position interest you most?

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In-Depth Questions For Instrumentation Professionals

Here are 51 role-specific questions the interviewer may ask you to evaluate your knowledge and skill level:

  1. What is process control?

  2. What are a transmitter and a 'smart' transmitter?

  3. Define the function of a controller.

  4. Name the process variables and their units of measurement.

  5. What is mathematical modelling?

  6. What are the primary elements and measuring instruments used for flow measurement?

  7. What are the different types of orifice plates? State their uses.

  8. How do you identify an orifice in a pipeline?

  9. What is the purpose of an orifice tab?

  10. Define interacting systems with an example.

  11. State Bernoulli's Theorem and explain its applicability.

  12. What is the force balance principle? State some of its advantages.

  13. What is the motion balance principle?

  14. Name different test inputs.

  15. What do you mean by self-regulation?

  16. Define thermocouple. What are its advantages?

  17. What are de-saturators?

  18. What is Fieldbus? What is the Foundation in Fieldbus?

  19. What is a control valve and its specifications? What are the different types of control valves?

  20. What is the use of single-seated valves and double-seated valves?

  21. What is a solenoid valve? Where is it applicable?

  22. What does a valve positioner do?

  23. Which seal liquid do you use for filling impulse lines on crude and viscous liquids?

  24. How is flow measured in square root?

  25. Name the different types of bourdon tubes.

  26. How to calibrate a D.P. transmitter?

  27. How to apply a D.P. transmitter to a close tank and an open tank?

  28. What are an open loop and a close loop?

  29. How to adjust 20 psi air supply to a transmitter?

  30. How do you identify the H.P. side or inlet of an orifice plate in line?

  31. What is the constant voltage unit?

  32. What is a zener diode and what is a voltage regulator?

  33. What is furnace draft control?

  34. Why is 4-20 mA preferred to a 0-20 mA signal?

  35. What is the relationship between proportional band and proportional gain?

  36. What are the two characteristics of a first-order process modelling?

  37. Mention two drawbacks of derivative action.

  38. Why is the electronic controller preferred to the pneumatic controller?

  39. How would you design a foolproof controller?

  40. Name different parts of a pressure gauge. Explain the use of a hairspring in a pressure gauge.

  41. What is the working principle of a magnetic meter?

  42. Explain the mechanism behind a turbine meter and a rotameter.

  43. Explain the working of an electronic level troll and an enraf level gauge.

  44. Explain the working of resistance temperature detectors (RTD).

  45. Why are thermowells used? What are the materials used in them?

  46. How do you calibrate a positioner?

  47. How is automatic reference junction compensation carried out in temperature recorders?

  48. Explain the ratio control system.

  49. How would you choose a differential range?

  50. What are the primary elements of measuring pressure? Which type of pressure can they measure?

  51. What type of pressure sensors can you use in pressure measurement?

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Instrumentation Interview Questions With Sample Answers

Knowing why interviewers ask certain questions, what they expect from an answer and what is the proper way to respond are key to a successful job interview. Here are four interview questions along with sample strategic answers to help you prepare yours:

1. Differentiate between two-wire, three-wire and four-wire transmitters.

The two-, three- and four-wire transmitters have a major role in the 4 to 20 Milliamp (mA) signal transmission system, which can regulate the current flow. These transmitters play an important part in transduction, amplification and signal conditioning. Knowing the difference between them shows you to know when to use which one. Explain briefly only the most important points of difference instead of trying to define the two-, three- and four-wire transmitters or transmitters in general.

Example: 'In a two-wire transmitter, one common cable transmits both power and signal. Data signal and power are always proportional to the ground in a three-wire transmitter. In a four-wire transmitter, two wires supply power and the other two transmit signals. These transmitters have higher accuracy and increasing levels of suitability for long-distance transmission with an increasing number of wires.'

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2. How can you measure temperature using a thermocouple?

A thermocouple is an electrical device for measuring temperature. This question essentially asks you to explain its working principle. Go into detail about the structure of a thermocouple and how that helps determine temperature. You can also explain the method of interpreting the voltage. You want to provide a comprehensive answer that demonstrates your in-depth understanding and clarifies the topic comprehensively.

Example: 'The two dissimilar electrical conductors of a thermocouple form electrical junctions at differing temperatures. When we heat or cool the junction, it generates a small voltage in the electrical circuit. This is a temperature-dependent voltage produced because of a thermoelectric effect. We can interpret this voltage by measuring the temperature at the reference junction with a direct-reading temperature sensor and then applying this cold-junction temperature measurement to the voltage reading. This way of determining the temperature measured by the thermocouple is called cold-junction compensation (CJC).'

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3. Briefly explain the importance of instrument calibration. How frequently is it required?

Calibration, a set of operations that compares a measurement device against a traceable reference standard or device, is a crucial task of an instrumentation technologist. Knowing the utility and importance of this task is essential when appearing for instrumentation interviews. Mention some core benefits of calibration and underline its necessity in your answer.

Example: 'Calibration defines the precision and efficiency of the measurement obtained using a machine component. As machinery drifts from its precision over time, especially when it uses specific techniques or tests particular parameters such as heat and humidity, calibrating them restores their precision back to the standard. Calibration keeps processes safe and helps reduce costs from manufacturing errors. Instruments ought to be calibrated based on manufacturer recommendations. It is necessary to calibrate instruments before and after a critical measuring project and also on a monthly, quarterly or biannual basis.'

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4. How can you contribute to this role if hired?

This is a common question that tests your understanding of the role and your confidence in your abilities to fulfil the responsibilities effectively. Responding with a well-constructed answer is imperative to increase your chances of impressing the interviewers. Start with explaining how you are going to execute the basic responsibilities of the role and then mention some unique personal attributes or soft skills which make you suitable for the position.

Example: 'As an instrumentation technologist, I am trained in troubleshooting and fixing equipment and instruments. My ability to analyse current equipment to identify areas of inefficiency and improvement can be an asset to this role. I can design and develop instrumentation to meet those requirements and increase process efficiency. In addition, I have excellent communication, adaptability and collaboration skills which make me perfectly equipped to work in diverse working conditions with various professionals, including electricians, pipe-fitters, power engineers and other technicians, to complete projects successfully on time.'

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