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Indiabix > Process Control and Instrumentation > Flashcards

Process Control and Instrumentation Flashcards

1
Q

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

A

500°C

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2
Q

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

A

Chromel-constantan

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3
Q

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

A

thermocouple

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4
Q

The frequency response of a first order system, has a phase shift with lower and upper bounds given by

A

0, π/2

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5
Q

The transfer function for a P-D controller is

A

Kc(1+τD s)

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6
Q

Pick out the most suitable instrument for measuring temperature in the range of -40 to 425°C.

A

bimetallic thermometer

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7
Q

Relationship between absorption/evolution of heat at the thermocouple junctions and the current flow in the circuit is given by __________ effect.

A

Peltier

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8
Q

Measurement of pressure in ammonia reactor is done by

A

Bourdon gauge

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9
Q

The temperature range for which copper resistance thermometer can be used is __________ °C

A

-200 to 150

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10
Q

Pirani gauge is used for the measurement of

A

high vacuum

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11
Q

__________ thermometer can not measure sub-zero (< 0° C) temperature.

A

Bimetallic

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12
Q

Starting temperature of optical radiation pyrometer is __________ °C.

A

800

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13
Q

The deflection of the free end of the bimetallic strips in a bimetallic thermometer with temperature is nearly

A

linear

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14
Q

Measurement of sub-zero Celcius temperature in industry is done most commonly by

A

resistance thermometers

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15
Q

Which of the following is not a mechanical pressure sensing element?

A

U-tube

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16
Q

Which of the following judges the accuracy of an instrument?

A

Static error

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17
Q

High temperature of around 2000°C of incandescent gas mantles is measured by a/an

A

radiation pyrometer

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18
Q

he unit step response of the transfer function 1/(s2 + 2s + 3)

A

has a damped oscillatory characteristics

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19
Q

What is the normal percentage of rhodium in platinum + rhodium element used in the thermocouple?

A

13

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20
Q

The transfer function of a process is 1/(16s2 + 8s + 4). If a step change is introduced into the system, then the response will be

A

under damped

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21
Q

An aneroid barometer measures the __________ pressure.

A

absolute

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22
Q

Thermal conductivity based continuous flue gas analyser makes use of varying thermal conductivity of the constituents of flue gases. Which of the following constituents of flue gases has the maximum thermal conductivity?

A

CO2

23
Q

Dilatometer is used to measure

A

contraction/expansion due to changes in temperature

24
Q

__________ stability method uses open loop transfer function.

A

Nyquist

25
Q

Composition of alloys can be determined by

A

polarograph

26
Q

Emf developed by a thermocouple while measuring a temperature of 400°C is 22 mV. The type of thermocouple used is

A

iron-constantan

27
Q

Out of the following temperature measuring instruments, the measurement accuracy will be minimum for the

A

optical pyrometer

28
Q

The deflection in diaphragm (which is used as pressure sensor in pneumatic and electronic instruments) is dependent on the metal thickness, its diameter (d) and shape & number of corrugations. Its deflection is proportional to

A

d^4

29
Q

Gas analysis is commonly done using the

A

thermal conductivity cell

30
Q

Thermal conductivity measurement is used for the determination of

A

CO2 percentage in the flue gas

31
Q

Process degree of freedom indicates __________ number of controllers to be used.

A

maximum

32
Q

Which of the following flow-metering instruments is an areameter?

A

Rotameter

33
Q

Which is the most suitable instrument for measuring pressure below 3 microns?

A

Ionisation gauge

34
Q

Bourdon tube is never made of

A

cast iron

35
Q

Flow rate measurement of hostile acids and alkalis can be most suitably done by a/an

A

magnetic flow meter

36
Q

Which of the following instruments is not used for measuring sub-zero (<0°) temperatures ?

A

Radiation pyrometer

37
Q

Emf developed by a thermocouple while measuring a temperature of 800°C is about 31 mV. The type of thermocouple used is

A

chromel-alumel

38
Q

Which of the following thermocouples is incapable of measuring sub-zero (i.e., < 0°C) temperature ?

A

Platinum-platinum + rhodium

39
Q

A first order system with unity gain and time constant τ is subjected to a sinusoidal input of frequency w = 1/τ. The amplitude ratio for this system is

A

1/(2^1/2)

40
Q

Dome temperature of blast furnace stove is most accurately measured by a

A

platinum-platinum/rhodium thermocouple

41
Q

Which of the following can measure temperatures in the range of - 20 to 300°C?

A

none of these

42
Q

“A control system is unstable, if the open loop frequency response exhibits an amplitude ratio exceeding unity at the crossover frequency.” This is __________ criterion.

A

Bode stability

43
Q

Positioning controllers are used for

A

high loads

44
Q

High temperature of around 2000°C of incandescent gas mantles is measured by a/an

A

radiation pyrometer

45
Q

Stabilising time for the controllers is the time required for the response to reach __________ percent of its ultimate value.

A

95

46
Q

__________ controller has the maximum stabilising time.

A

PI

47
Q

Emission spectroscopy is used for

A

solids and metal analysis

48
Q

Operating range of a temperature measuring instrument is 800 to 1600°C. It could be a/an __________ pyrometer.

A

photoelectric

49
Q

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

A

load

50
Q

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

A

controlled

51
Q

What is the Laplace transform of impulse input having magnitude ‘X’ ?

A

1

52
Q

Which of the following filled system expansion thermometers has the lowest positive temperature measurement capability ?

A

Alcohol in glass thermometer.

53
Q

Which of the following is not suitable for measuring the temperature of a red hot object in the range of 800 - 1600°C ?

A

thermocouples

Indiabix (3 decks)

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