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Process Control and Instrumentation MCQ Questions & Answers

Process Control and Instrumentation MCQs : This section focuses on the "Process Control and Instrumentation". These Multiple Choice Questions (MCQs) should be practiced to improve the Process Control and Instrumentation skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.




Question 1

In a shell and tube heat exchanger, the flow rate of heating/cooling fluid is the __________ variable.

A. load
B. controlled
C. manipulated
D. none of these

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Question 2

Pick out the first order system from among the following.

A. Damped vibrator.
B. Mercury in glass thermometer kept in boiling water.
C. Interacting system of two tanks in series.
D. Non-interacting system of two tanks in series.

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Question 3

The __________ of a vapor pressure thermometer is a functioning element.

A. pointer
B. bourdon tube
C. bulb
D. none of these

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Question 4

Which of the following controllers has the least maximum deviation ?

A. P-controller
B. P-I controller
C. P-I-D controller
D. P-D controller

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Question 5

Strain gage pressure transducers are used to measure __________ pressures.

A. gage as well as vacuum
B. absolute as well as differential
C. both (a) and (b)
D. neither (a) nor (b)

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Question 6

Flapper nozzle is used in a/an __________ controller.

A. electronic
B. hydraulic
C. pneumatic
D. none of these

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Question 7

Select the correct statement from the following.

A. The frequency response of a pure capacity process is unbounded.
B. The phase lag of a pure time delay system decreases with increasing frequency.
C. The amplitude ratio of a pure capacity process is inversely proportional to frequency.
D. The amplitude ratio of a pure time delay system increases with frequency.

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Question 8

A proportional controller with a gain of Kc is used to control a first order process. The offset will increase, if

A. Kc is reduced.
B. Kc is increased.
C. integral control action is introduced.
D. derivative control action is introduced.

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Question 9

In a single tank system, the transfer function of level to inlet flow rate is

A. R/TS
B. R/(TS + 1)
C. l(TS + l)
D. 1/TS

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Question 10

The operation of a rotameter is based on

A. variable flow area.
B. rotation of a turbine.
C. pressure drop across a nozzle.
D. pressure at a stagnation point.

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Question 11

Thermistor, which has high temperature co-efficient of resistivity, is used as the sensing element in resistance thermometer. It is a/an

A. insulator
B. conductor
C. solid semi-conductor
D. liquid semi-conductor

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Question 12

A magnetic flowmeter is

A. based on the principle of Faraday's law.
B. capable of measuring the flow rate of slurries and electrolytes.
C. based on the linear relationship between the fluid flow rate and the induced voltage.
D. all (a), (b) and (c).

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Question 13

Which of the following is a desirable characteristic of an instrument ?

A. High drift
B. High fidelity
C. High measuring lag
D. Poor reproducibility

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Question 14

Emf developed by a thermocouple, while measuring a temperature of 600°C is about 5.5 mV. The type of thermocouple used is

A. chromel-alumel
B. iron-constantan
C. platinum-platinum+rhodium
D. either (a), (b) or (c)

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Question 15

The temperature of tempering oil baths maintained at 400°C during heat treatment of steel is measured by a/an __________ thermocouple.

A. chromel-alumel
B. iron-constantan
C. platinum-platinum/rhodium
D. none of these.

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Question 16

The closed loop pole of a stable second order system could be

A. both real and positive.
B. complex conjugate with positive real parts.
C. both real and negative.
D. one real positive and the other real negative.

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Question 17

Response of a system to a sinusoidal input is called __________ response.

A. impluse
B. unit step
C. frequency
D. none of these

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Question 18

The function of a transducer is to

A. modify the input signal.
B. amplify the input signal.
C. convert the primary signal into a more useful quantity, usually an electric impulse.
D. codify/decodify the input signal.

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Question 19

Which of the following is not the triple point of water ?

A. 32°R
B. 273°K
C. 492°R
D. 32°F

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Question 20

Continuous shell temperature measurement in a liquid-liquid heat exchanger is done by a

A. thermocouple
B. reistance thermometer
C. mercury in glass thermometer
D. vapor pressure thermometer

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Question 21

Which of the following measurements can be made by the measurement of emf ?

A. pH value
B. Degree of hydrolysis
C. Composition of complex ions
D. All (a), (b) & (c)

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Question 22

Transfer function of transportation lag is

A. eTS
B. e-TS

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Question 23

Load cells are used for the measurement of

A. stress
B. weight
C. strain
D. velocity

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Question 24

Smoke density of the flue gas going out of the chimney is measured by a

A. polarograph
B. thermal conductivity meter
C. photo electric cell
D. chromatograph

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Question 25

Nichol's chart deals with

A. A.R. vs. phase lag of first order.
B. A.R. vs. phase lag of second order.
C. closed loop values vs. open loop values.
D. frequency response values of controllers.

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Question 26

Pick out the wrong statement.

A. O2, NO and NO2 exhibit paramagnetic properties as a result of unpaired electrons.
B. CO2 is the strongest paramagnetic gas.
C. Paramagnetic susceptibility of gases decreases with temperature.
D. Paramagnetic susceptibility of gases permits the measurement of their concentration.

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Question 27

Which of the following is the dynamic characteristics of an instrument ?

A. Reproducibility
B. Sensitivity
C. Dead zone
D. Fidelity

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Question 28

Which of the following relates the emf. generated in a single homogeneous wire to the temperature difference ?

A. Peltier effect
B. Thomson effect
C. Seebeck effect
D. none of these

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Question 29

Which of the following relates the absorption & evolution of heat at the junctions of a thermocouple to the current flow in the circuit?

A. Seebeck effect
B. Peltier effect
C. Joule heating effect
D. Thomson effect

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Question 30

Instrumentation in a plant offers the advantage of

A. greater safety of operation
B. better quality of product
C. greater operation economy
D. all (a), (b) and (c)

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Question 31

Zirconia probe is used for the continuous measurment of __________ flue gases going out of the furnace.

A. oxygen in
B. carbon dioxide in
C. carbon monoxide in
D. temperature of

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Question 32

__________ is undesirable in thermocouples used in industries,

A. Linear relation of emf to temperature
B. Corrosion resistance
C. Oxidation resistance
D. Non-linear relation of emf to temperature

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Question 33

For an input forcing function, X(t) = 2t2, the Laplace transform of this function is

A. 2/s2
B. 4/s2
C. 2/s3
D. 4/s3

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Question 34

Typical specifications for design stipulates the gain margin and phase margin to be respectively

A. > 1.7 and > 30°
B. < 1.7 and > 30°
C. < 1.7 and < 30°
D. > 1.7 and < 30°

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Question 35

Dilute wine was used as a thermometric liquid initially to develop temperature scale. First emperical temperature scale developed was the __________ scale.

A. Kelvin
B. Centigrade
C. Fahrenheit
D. Reaumer

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Question 36

The __________ of a vapor pressure thermometer is a secondary element.

A. pointer
B. Bourdon tube
C. bulb
D. none ofthese

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Question 37

Pick out the one which is a first order instrument.

A. Mercury in glass thermometer (without any covering or air gap).
B. Bare metallic thermometer.
C. Bare vapor pressure thermometer.
D. All (a), (b) and (c).

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Question 38

Compositional analysis of __________ is done using mass spectrometer.

A. an isotope
B. natural gas
C. a solid
D. an alloy

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Question 39

Thermal conductivity measurement com-prises the working principle of a

A. CO2 analyser
B. polarimeter
C. spectrometer
D. chromatograph

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Question 40

Which of the following is an undesirable dynamic characteristic of an instrument ?

A. Reproducibility
B. Dead zone
C. Time lag
D. Static error

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Question 41

The maximum service temperature for fibre glass used as thermocouple wire insulation material is __________ °C.

A. 250
B. 500
C. 750
D. 1000

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Question 42

Temperature measuring instruments are standardised mostly with __________ points of pure substances.

A. melting
B. boiling
C. both (a) & (b)
D. neither (a) nor (b)

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Question 43

Working principle of radiation pyrometer is based on the

A. Wien's law
B. Kirchoffs law
C. Stafan-Boltzman law
D. Seebeck effect

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Question 44

Which of the following temperature measuring instruments need not touch the object whose temperature is being measured ?

A. Radiation/infrared pyrometer
B. Filled system thermometer
C. Mercury in glass thermometer
D. Thermo electric pyrometer

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Question 45

Which of the following thermocouples will give the highest output for the same value of hot and cold junction temperature ?

A. Platinum-platinum + rhodium.
B. Iron-constantan.
C. Chromel-constantan.
D. All will give the same output.

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Question 46

A negative gain margin expressed in decibels means a/an __________ system.

A. stable
B. unstable
C. critically damped
D. none of these

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Question 47

Volumetric expansion is the working principle of the __________ thermometers.

A. mercury in glass
B. constant volume gas
C. vapor pressure
D. bimetallic

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