HomeInstrumentation RelatedInterview Questions on Instrumentation Part-1

Interview Questions on Instrumentation Part-1

Introduction: –

All listed questions are based on my own interview experience. so here are the Top Interview Questions on Instrumentation Part-1.

My goal is to make instrument engineers capable enough to get their field job.

In this move, I will try to give all materials and references for getting your best job in the instrumentation field.


Top Interview Questions on Instrumentation Part-1


1. Define instrumentation?

Ans: –

Instrumentation is a combination of measuring instruments that indicate, measure, and record process variables in industries.


2. What is RTD? Explain.

Ans: –

RTD is a resistance temperature detector. It works on the principle of change in resistance due to temperature change.

And it has a positive temperature coefficient which means when temperature increases the Value of resistance increases.



3. What are sensors and types of sensors?

Ans: –

A sensor is a device that takes physical input from the environment and converts it into a single device that humans or machines will interact with.


4. What is the difference between Transducer, Sensor, Transmitter, And converter?


Difference between sensors, Transducers, and transmitter

Ans: –

1. Transducer

A transducer is a device that converts one type of energy signal into another type of energy signal. Ex- LVDT is a transducer it converts mechanical movement into electrical output.

2. Sensor

A sensor is a device that takes physical input from the environment and converts it into a single one that humans or machines will interact with. Ex- Proximity sensor

3. Transmitter

A transmitter is a device that applies signal conditioning and scaling on the transducer signal and converts it into the industrial stranded signal.

Ex- temperature transmitter that converts thermocouple millivolt signal into 4-20mA signal

4. Converter

The converter is responsible for converting one type of industrial standard signal into another type of industrial standard signal.

The Ex- I/p converter converts a 4-20mA signal into a 3-15psi pressure signal.


5. What is the difference between converter and transmitter?

Ans: –

1. Transmitter

A transmitter is a device that applies signal conditioning and scaling on the transducer signal and converts it into the industrial stranded signal.

Ex- temperature transmitter that converts thermocouple millivolt signal into 4-20mA signal

2. Converter

The converter is responsible for converting one type of industrial standard signal into another type of industrial standard signal.

The Ex- I/p converter converts a 4-20mA signal into a 3-15psi pressure signal.


5. Why does the industry use a 4-20mA standard signal instead of 0-20mA?

Ans: –

In 0-20mA signal Controller does not distinguish between the Control signal or Cable break, when a 4-20mA signal is used instead of 0-20mA When the controller gets a 0mA signal then the controller easily finds out it is a wire Fault.


6. What is signal conditioning?

Ans: –

Signal conditioning is a process of manipulating an analog signal in such a way that signal meets its requirement according to need.


7. Output of thermocouple?

Ans: –

The output of the thermocouple is in mV (Millivolt) on the principle of the see-back effect. The inverse effect of the see-beck effect is the Peltier effect.


8. Types of Level, Flow, Temperature, and Pressure Transmitter?

Ans: –

1. Level

  • Capacitive type
  • Ultrasonic type
  • Radar type
  • Radiation type
  • Differential pressure type

2. Flow

  • Magnetic type
  • Vortex type
  • Ultrasonic type
  • venturi type
  • Pitot type
  • Orifice type
  • Turbine type
  • Coriolis mass flow type
  • Thermal mass flow type

3. Temperature

  • Thermocouple type
  • RTD type

4. Pressure

  • Differential pressure type

9. Types of orifice Plats?

Ans: –

  • Concentric
  • Eccentric
  • Segmented


10. What is pt-100? Why is it called pt-100?

Ans: –

Pt 100 is a commonly used RTD. It is made of platinum and it has 100 ohms of resistance at 0*C

That’s why it is called pt-100.


11. What is absolute pressure?

Ans: –

Absolute pressure is the sum of Guage pressure and atmospheric pressure.


12. What are common flow transducers and their working principles?

Ans: –

1. Differential pressure

  • Orifice meter
  • Venturi meter
  • Pitot tube

Above all, Bernoulli’s theorem of energy.


13. What is the valve coefficient?

Ans: –

The volume (in US gallons) of water at 60°F will flow per minute through a valve with a pressure drop of 1 psi across the valve.


14. What is the difference between 2 wire, 3-wire, and 4-wire transmitters?

Ans: –

1. 2-wire

2- wire transmitter has power and signal on the same line

2. 3-wire

in 3-wire combination power and signal connected to a separate line. but the ground is common between source and panel.

4. 4-wire

In the four-wire configuration, the supply line and the signal line are fully isolated from each other. to reduce noise in the signal line.


15. Difference between thermocouple, RTD, and thermistor?

Ans: –

Thermistor: – Resistance changes with temperature but it is nonlinear. Used where high sensitivity is required.

RTD: – Resistance changes with temperature linearly. It has a positive temperature Coefficient.

Thermocouple: – It works on the principle of the Seeback effect. It gives output in Millivolts. It has a very high range so it is most commonly used in industry. Cold junction compensation.


16. Why is 3 to 15 psi used as standard instead of 0 to 15 psi?

Ans: –

It’s because below 3 psi is very low pressure which is hard to control or manipulate and also u have to provide a vacuum to allow for calibration and measurement hysteresis & repeatability errors.


17. Most common process parameters used in industry?

Ans: –

  • Pressure
  • Temperature
  • Flow
  • Level
  • PH

18. What is a smart transmitter?

Ans: –

The smart transmitter is an advanced version of the transmitter. The smart transmitter has a microprocessor and it provides facilities like signal conditioning, environmental disturbance reduction, self-calibrate, and self-diagnosing facilities.


19. What is the difference between Profibus PA and Profibus-DP?

Ans: –

1) Profibus DP: – In Profibus-DP Protocol all I/O modules of PLC are transferred to the factory floor and using a single data cable all data will transfer to the plc.

2)Profibus-PA: – In Profibus PA all the factory floor instrument is connected to the signal bus cable and passed all single to segment coupler for converting Profibus-PA signal into Profibus DP signal.


20. What is the HART protocol?

Ans: –

The full form of HART protocol is Highway Addressable Remote Transducer. It is a communication Protocol used for connecting transmitters to controllers.

It is a hybrid protocol. It means for communication it will use analog and digital signals on a single communication bus.


EndNote: –

Many of the interview questions come from your resume. It includes an area of interest you mentioned in your resume and your final year engineering project.

In this post, I will regularly update and give the latest information as possible so if you have any questions, please let me know in the comment section.




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4 COMMENTS

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