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indiabix > Process Control and Instrumentation > Flashcards

Process Control and Instrumentation Flashcards

1
Q

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

Reproducibility
Dead zone
Time lag
Static error

A

Time lag

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2
Q

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

A

32°R

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3
Q

Pick out the one which is a first order instrument.

Mercury in glass thermometer (without any covering or air gap).

Bare metallic thermometer.

Bare vapor pressure thermometer.

A

All of these

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4
Q

Load cells are used for the measurement of

A

weight

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5
Q

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

A

Fidelity

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6
Q

Pick out the wrong statement.

O2, NO and NO2 exhibit paramagnetic properties as a result of unpaired electrons.

CO2 is the strongest paramagnetic gas.

Paramagnetic susceptibility of gases decreases with temperature.

Paramagnetic susceptibility of gases permits the measurement of their concentration.

A

CO2 is the strongest paramagnetic gas.

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7
Q

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

pointer
bourdon tube
bulb

A

pointer

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8
Q

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

A

unstable

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9
Q

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

A

solid semi-conductor

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10
Q

Flapper nozzle is used in a/an __________ controller.

A

pneumatic

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11
Q

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

A

> 1.7 and > 30°

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12
Q

Working principle of radiation pyrometer is based on the

A

Stefan-Boltzman law

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13
Q

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

A

Thomson effect

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14
Q

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

A

Fahrenheit

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15
Q

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

A

R/(TS + 1)

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16
Q

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

A

High fidelity

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17
Q

The operation of a rotameter is based on

A

variable flow area.

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18
Q

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

A

iron-constantan

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19
Q

Instrumentation in a plant offers the advantage of

greater safety of operation
better quality of product
greater operation economy
all (a), (b) and (c)

A

all (a), (b) and (c)

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20
Q

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

A

Radiation/infrared pyrometer

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21
Q

Thermal conductivity measurement com-prises the working principle of a

A

CO2 analyser

22
Q

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

A

frequency

23
Q

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

A

both real and negative.

24
Q

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

A

photo electric cell

25
Q

Transfer function of transportation lag is

A

e^(-TS)

26
Q

Temperature measuring instruments are standardised mostly with __________ points of pure substances.
melting
boiling
both (a) & (b)

A

both melting and boiling

27
Q

Pick out the first order system from among the following.

Damped vibrator.

Mercury in glass thermometer kept in boiling water.

Interacting system of two tanks in series.

Non-interacting system of two tanks in series.

A

Mercury in glass thermometer kept in boiling water.

28
Q

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

A

500

29
Q

Which of the following controllers has the least maximum deviation ?

A

P-D controller

30
Q

Volumetric expansion is the working principle of the __________ thermometers.

A

mercury in glass

31
Q

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

pH value

Degree of hydrolysis

Composition of complex ions
All (a), (b) & (c)

A

All

32
Q

A magnetic flowmeter is

based on the principle of Faraday’s law.

capable of measuring the flow rate of slurries and electrolytes.

based on the linear relationship between the fluid flow rate and the induced voltage.

all (a), (b) and (c).

A

All

33
Q

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

A

oxygen in

34
Q

Strain gage pressure transducers are used to measure __________ pressures.

gage as well as vacuum

absolute as well as differential

both (a) and (b)

A

both (a) and (b)

35
Q

The transfer function for a PID controller is (where, τ i is the integral (reset) time and τD is the derivative time.)

A

Kc(1+1/( τs)+Tds)

36
Q

Compositional analysis of __________ is done using mass spectrometer

A

an isotope

37
Q

The function of a transducer is to

A

convert the primary signal into a more useful quantity, usually an electric impulse.

38
Q

Nichol’s chart deals with

A

closed loop values vs. open loop values.

39
Q

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

Platinum-platinum + rhodium.

Iron-constantan.

Chromel-constantan.

A

Chromel-constantan.

40
Q

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.

41
Q

The symbol for “capillary line” in instrumentation diagram is

A

—x–x–x–x–

42
Q

__________ is undesirable in thermocouples used in industries,

A

Non-linear relation of emf to temperature

43
Q

Select the correct statement from the following.

The frequency response of a pure capacity process is unbounded.

The phase lag of a pure time delay system decreases with increasing frequency.

The amplitude ratio of a pure capacity process is inversely proportional to frequency.

The amplitude ratio of a pure time delay system increases with frequency.

A

The amplitude ratio of a pure capacity process is inversely proportional to frequency.

44
Q

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

A

4/t^3

45
Q

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

A

thermocouple

46
Q

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

A

Bourdon tube

47
Q

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

A

platinum-platinum+rhodium

48
Q

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

A

Peltier effect

49
Q

The second order system with the transfer function 4/(s^2+2s+4) has a damping ratio of

A

0.5

50
Q

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

A

manipulated

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