Process Control and Instrumentation

Question 1

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

Answer 1

500°C

Question 2

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

Answer 2

Chromel-constantan

Question 3

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

Answer 3

thermocouple

Question 4

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

Answer 4

0, π/2

Question 5

The transfer function for a P-D controller is

Answer 5

Kc(1+τD s)

Question 6

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

Answer 6

bimetallic thermometer

Question 7

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

Answer 7

Peltier

Question 8

Measurement of pressure in ammonia reactor is done by

Answer 8

Bourdon gauge

Question 9

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

Answer 9

-200 to 150

Question 10

Pirani gauge is used for the measurement of

Answer 10

high vacuum

Question 11

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

Answer 11

Bimetallic

Question 12

Starting temperature of optical radiation pyrometer is __________ °C.

Answer 12

800

Question 13

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

Answer 13

linear

Question 14

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

Answer 14

resistance thermometers

Question 15

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

Answer 15

U-tube

Question 16

Which of the following judges the accuracy of an instrument?

Answer 16

Static error

Question 17

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

Answer 17

radiation pyrometer

Question 18

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

Answer 18

has a damped oscillatory characteristics

Question 19

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

Answer 19

13

Question 20

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

Answer 20

under damped

Question 21

An aneroid barometer measures the __________ pressure.

Answer 21

absolute

Question 22

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?

Answer 22

CO2

Question 23

Dilatometer is used to measure

Answer 23

contraction/expansion due to changes in temperature

Question 24

__________ stability method uses open loop transfer function.

Answer 24

Nyquist

Question 25

Composition of alloys can be determined by

Answer 25

polarograph

Question 26

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

Answer 26

iron-constantan

Question 27

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

Answer 27

optical pyrometer

Question 28

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

Answer 28

d^4

Question 29

Gas analysis is commonly done using the

Answer 29

thermal conductivity cell

Question 30

Thermal conductivity measurement is used for the determination of

Answer 30

CO2 percentage in the flue gas

Question 31

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

Answer 31

maximum

Question 32

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

Answer 32

Rotameter

Question 33

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

Answer 33

Ionisation gauge

Question 34

Bourdon tube is never made of

Answer 34

cast iron

Question 35

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

Answer 35

magnetic flow meter

Question 36

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

Answer 36

Radiation pyrometer

Question 37

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

Answer 37

chromel-alumel

Question 38

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

Answer 38

Platinum-platinum + rhodium

Question 39

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

Answer 39

1/(2^1/2)

Question 40

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

Answer 40

platinum-platinum/rhodium thermocouple

Question 41

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

Answer 41

none of these

Question 42

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

Answer 42

Bode stability

Question 43

Positioning controllers are used for

Answer 43

high loads

Question 44

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

Answer 44

radiation pyrometer

Question 45

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

Answer 45

95

Question 46

__________ controller has the maximum stabilising time.

Answer 46

PI

Question 47

Emission spectroscopy is used for

Answer 47

solids and metal analysis

Question 48

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

Answer 48

photoelectric

Question 49

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

Answer 49

load

Question 50

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

Answer 50

controlled

Question 51

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

Answer 51

1

Question 52

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

Answer 52

Alcohol in glass thermometer.

Question 53

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

Answer 53

thermocouples