Instrumentation Interview Questions and Answers

Instrumentation Interview Questions and Answers

Instrumentation Interview Questions and Answers

Q-1 – Which parameters are variable in the process?

AnswerProcess has variable parameters.

1 – Pressure

2 – Flow

3 – Temperature

4 – Quality

5 – Level

Q-2 – Which equipment is used for flow measurement?

Answer– For flow measurement

1 – Venturi Tube

2 – Orifice Plate

3 – Pilot Tube

4 – News

5-flow nozzle

Q-3 – Which type of orifice plate?

Answer– There are four main types of orifice plate

1 – Segmental

2 – Concentric

3 – Quadrant Age

4 – Accentric

Q-4 – How will we know if there is an Orifice plate in the pipeline?


There is an orifice tab, which welds with the orifice plate. Due to which the outer becomes thicker. And from this we get the indication that the line has been Orifice.

Q-5 – Orifice Tab Q is installed?

Answer- Reason for setting up Orifice Table

We get the Indication of Orifice tab in 1 – line.

2 – There is a marking of the Diameter above it.

3 – His material is also written in Orifice.

4 – The tag number of Orifice is mentioned above.

5 – There is also a marking of the inlet of Orifice.

Q-6 – How is H.P (inlet) side detected in Orifice?

Answer – The orifice has a marking of the H.P (inlet) side. Wherever we come to know the inlet side.

Q-7– How to calibrate -D.P transmitter?

Answer– Transmitter calibration steps are below

1 – First of all we will adjust the zero of the transmitter.

2 – Static pressure test – In which the transmitter is given the same pressure from both sides. After giving presser, we should get zero on DP.

3 – Will do vacuum test – Uniform vacuum is given from both sides. At that time also DP should get zero.

4 – Pressure is adjusted by giving pressure on high side.

5 – Zero can adjust again if needed.

Q-8 – The flow in the transmitter is not high, how will they check?


1 – We will flush the transmitter. In this, HP will flush the LP Impulse line.

2 – Zero will adjust by opening the equalization valve.

3 – Will check line jam on LP side. And clean it.

4 – Will check leakage in it.

5 – Calibration will do.

Q-11 – Describe the type of pressure? Types of Pressure?

Answer – There are three main types of pressure

1 – Atmospheric Pressure

2 – gauge pressure

3 – Absolute Pressure

Q-12 – What is absolute pressure?

Answer – The current pressure in any system is called absolute pressure. It can also be understood from the formula below.

Absolute Pressure = Gauge Pressure + Atmospheric Pressure

Q-13 – What is atmospheric pressure?

Answer – The pressure exerted by the pressure of atmosphere is called atmospheric pressure. At high altitudes, the air pressure is low, hence the atmospheric pressure is also low. Usually it is 1KG / CM2.

Q-14 – What is gauge pressure?

Answer– Whatever pressure we see above the atomospheric pressure is called a gauge pressure. Atmospheric pressure is normally 1KG / CM2.

Q15 – What is vacuum pressure?

Answer- Even where there is less pressure than atomospheric pressure, it will be called vacuum pressure.

Q-16 – Which measuring  instrument is used to measure pressure.

Answer- The instrument given below is used to do pressure majors.

1 – Diaphragm

2 – Burden Tube

3 – Bello

4 – capsule

5 – Pressure Spring

Q-17 – Pressure gauge works on which principle?

Answer- Pressure gauge works on the principle of “hook lo”. Measuring the stress on elastic is called hook of low.

Q-18 – Describe the parts of the pressure gauge. Parts of pg


1 – C ‘Type Burden Tube

2 – Sector Gear

3 – Connecting Link

4 – Pinion Gear

5 – Pointer

6 – Hair Spring

7 – Dial

Q-19 – Describe the different method of measuring temperature?

Answer – There are two main methods of measuring temperature.

1 – Mechanical method

2 – Electrical method

Methods of measuring temperature in mechanical method

1 – Temperature can be measured by placing mercury in a glass thermometer.

2 – Bimetallic thermometer can measure temperature.

3 – Pressure Spring Thermometer

Methods of temperature measurement by electrical method

1 – Can check temperature with thermocouple.

2 – RTD – Resistance can measure temperature with temperature detector.

Q-20 – What is the meaning of PT-100 and PT-1000?

Answer -PT-100 means PT means platinum, and 100 means 100 ohm per 00 C temperature. Likewise, PT means 1000 in platinum, and 1000 means 1000 ohm per 00 C temperature.

Q-21 – Why is thermowell applied?

Answer – There are many such applications in the factory, where we cannot bring direct temperature sensor into contact. Thermovale is used to measure the temperature of such place. In addition, there is no chemical effect on the sensor, so no thermosevel is also preferred. Applying a thermowell can protect the sensor from physical damage during operation.

Q-22 – Which materials are used for thermowell?

Answer- The main four materials are used for thermowells.

1 – Alloy Steel

2 – Stainless Steel

3 – Inconel

4 – Monel

Q-23 – Who is used to major low temperature?

Answer- RTD (resistance temperature detector) is used to measure low temperature.

Q-24 – What does skin temperature thermocouple mean?

Answer – Touch with direct material. It does not use any type of thermowell, hence it is called skin thermocouple. It is used to measure the temperature of heater, furnace and fuel gas.

Q-25 – What is the difference between thermocouple and twin wire RTD?

1 – In wire RTD the color of the wire is red and white. Whereas the wire of a thermocouple is the basis of its type.

The 2-thermocouple has a plus and minus signal. There is no such signal in RTD.

3-The thermocouple increases the temperature as the temperature increases. The temperature in RTD increases as the resistance increases. On the basis of the vault and resistance, we can also detect RTD and thermocouple.

Q-26 – What are the active and passive components in instrumentation?

Answer- The instrument which needs an ode of spring for operation. It is called Active Component.

For example – devices like transmitter, control valve, PID controller and indicator are called active components.

The device, which does not require any hymn outside, is called a passive component.

For example – devices like RTD (resistance temperature detector), pressure gauge, temperature gauge, thermocouple do not need any external hymn.

Q-27 – Which type of pneumatic control valve is?

Answer – The types of pneumatic control valves are given below.

1 – globe valve

2 – Butter Fly Valve

3 – Ball valve (A) On off valve (B) Continue open valve

4 – Air to open valve

5-year then close valve

Q-28 – How is the signal of temperature from field to PLC, DCS and controller?


The signal of the temperature matches both the RTD and the thermocouple. It is transferred in two ways.

1 – Direct – In this the wire of RTD and thermocouple is directly connected to PLC, DCS and controller.

2 – Using the temperature transmitter – The temperature transmitter first converts the signal from the RTD and thermocouple to 4 to 20 MA. This signal is sent to the PLC, DCS and controller.

Instrumentation Interview Questions and Answers

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Instrumentation Interview Questions and Answers

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