Try mock test questions on GATE Electronics and Instrumentation Engineering and check questions with corresponding answers.
GATE Instrumentation Questions
1. Which of the following is a desirable characteristic of an instrument?
A) high fidelity
B) poor reproducibility
C) high drift
D) high-temperature lag
2. Offset
A) does not vary with time
B) varies exponentially with time
C) varies as square of the time
D) varies with time
3. Cascade control is
A) used when changes in process conditions cause serious upsets in controlled variable
B) useful to control flow from temperature
C) the continuous adjustment of the set point index of an automatic control loop by 2 primary (master) controller
D) all of the answers
4. Which of the following controllers has the least maximum deviation?
A) P controller
B) PI controller
C) PID controller
D) PD controller
5. The flow rate through an orifice is
A) proportional to the square root of pressure differential
B) inversely proportional to the square root of pressure differential
C) proportional to the pressure differential
D) inversely proportional to the square root of pressure differential
6. The flow rate of a liquid containing heavy solids (e.g. sand) can be best measured by
A) rotameter
B) pitot tube
C) concentric orifice
D) eccentric orifice
7. Thermal wells are used in temperature measurement to
A) reduce measuring lag
B) increase the fidelity
C) guard against corrosive and oxidizing action on thermocouple materials
D) increase the sensitivity
8. E.m.f. generated by thermocouples is of the order of
A) bi-metallic thermometer
B) volts
C) millivolts
D) microvolts
9. Interfacial level in the pressure vessel is measured by
A) Bourdon gauge
B) float
C) U-tube manometer
D) manometers of float type
10. Pick out the most suitable instrument for measuring temperature in the range of – 40 to 800 °F.
A) none of the answers
B) mercury thermometer
C) bimetallic thermometer
D) radiation pyrometer
11. Measurement of pressure in the ammonia reactor is done by
A) Pirani gauge
B) Bourdon gauge
C) U-tube manometer
D) Inclined tube manometer
12. The mode used for transmitting signal for one-kilometer distance is
A) all of the answers
B) electronic
C) pneumatic
D) hydraulic
13. Bode stability method uses
A) either open-loop transfer function or closed-loop transfer function
B) closed-loop transfer function
C) open-loop transfer function
D) neither open-loop transfer function nor closed-loop transfer function
14. Weir valve is used for
A) acids
B) neutral solutions
C) bases
D) slurries
15. A simple pitot tube measures
A) point velocity
B) maximum velocity
C) average velocity
D) static pressure
16. The final control element is a
A) signal
B) valve
C) switch
D) both valve & switch
17. On-off control
A) all of the answers
B) is a two-position (fully open or fully closed) control adequate to control a process with slow reaction rate and minimum dead time or transfer lag
C) fully closes the final control element when the measured variable is above the setpoint
D) fully opens the final control element when the measured variable is below the setpoint
18. V-notch is used to measure the flow rate of a liquid in
A) vertical pipeline
B) a non-circular cross-section closed channel
C) an open channel
D) horizontal pipeline
19. Process degrees of freedom
A) gives no idea of controllers
B) indicates the minimum number of the controller to be used
C) indicates the maximum number of the controller to be used
D) determines the both maximum and minimum number of controllers to be used
20. What is the Laplace transform of sint?
A) 1/S2+1
B) S/1+S2
C) 1/S2-1
D) S/S2-1
21. In an exothermic chemical reactor, the manipulated variable is the flow rate of
A) product
B) hot fluid
C) coolant
D) reactant
22. Pick out the first-order system from among the following
A) mercury in glass thermometer kept in boiling water
B) non-interacting system of two tanks in series
C) damped vibrator
D) interacting system of two tanks in series
23. Thermocouple is suitable for measuring
A) both high and low temperatures
B) very low temperatures only
C) very high temperatures only
D) liquid temperatures only
24. Flapper nozzle is a
A) pneumatic controller
B) hydraulic controller
C) electronic controller
D) both the pneumatic controller and a hydraulic controller
25. Optimal activity of a solution can be determined using a
A) dilatometer
B) polarograph
C) polarimeter
D) refractometer
26. The symbol for “capillary line” in instrumentation diagram is
27. pH meter has
A) two cells
B) no cell
C) three cells
D) one cell
28. Psychrometer determines
A) moisture content of solids
B) hygroscopic nature of solids
C) humidity of gases
D) water of crystallization
29. Laplace transform method is used for
A) both linear behavior and non-linear behavior
B) linear behavior
C) neither linear behavior nor non-linear behavior
D) non-linear behavior
30. A controller action in which there is a continuous relation between the value of the controlled variable and the value of the output signal of the controller is called
A) proportional action
B) derivative action
C) integral action
D) proportional-derivative action
31. Continuous measurement of specific gravity of a liquid is done by
A) both hydrometer & displacement meter
B) contact-type electric indicators
C) displacement meter
D) hydrometer
32. The pressure of 0.01 psi (absolute) can be measured by
A) Bourdon gauge
B) Pirani gauge
C) Ionization gauge
D) Mcleod gauge
33. Nichel’s chart deals with
A) A.R. vs. phase lag of first order
B) closed loop values vs. open loop value
C) frequency response values of controllers
D) A.R. vs. phase lag of second order
34. The transfer function of the first order system is
A) 1/Ts
B) S/(Ts+1)
C) 1/S
D) 1/(Ts+1)
35. Gas analysis is commonly done using
A) X-ray diffraction
B) mass spectrometer
C) emission spectrometer
D) thermal conductivity cell
36. The critically damped system means that the damping coefficient is
A) <1
B) 1
C) >1
D) 0
37. Stalagmometer is used for the measurement of
A) surface tension
B) optical activity
C) refractive index
D) kinematic viscosity
38. Use of I-control along with P-control facilitates
A) reduction of stability time
B) both reduction of offset & reduction of stability time
C) elimination of offset
D) reduction of offset
39. The steady-state ratio of the change of proportional controller output variable and the change in the actuating signal is called
A) reset rate
B) integral action
C) proportional sensitivity
D) rangeability
40. Cascade control means
A) one feed-back loop
B) feedforward control
C) on-off control
D) more than one feedback loop
41. Use of pilot in transmission (pneumatic) is to
A) change the flow of air
B) adjust the signal
C) all of the answers
D) speed up signal
42. The pressure of 0.0001 absolute psi can be measured by
A) Mcleod gauge
B) Bourdon gauge
C) Thermocouple gauge
D) Pirani gauge
43. The degree to which an instrument indicates the changes in a measured variable without dynamic error is called
A) speed of response
B) fidelity
C) its static characteristics
D) reproducibility of instrument
44. Minute depression of freezing point of a liquid solvent or addition of a solid solute can be best measured by
A) Beckman thermometer
B) mercury thermometer
C) dilatometer
D) bimetallic thermometer
45. Phase lag of the sinusoidal response of a first-order system is
A) 120°
B) 90°
C) 30°
D) 180°
46. The valve used to supply oil to the burner is
A) gate valve
B) both gate valve and butterfly valve
C) butterfly valve
D) rotary plug valve
47. The frequency at which the maximum amplitude ratio is attained is called
A) corner frequency
B) natural frequency
C) cross-over frequency
D) resonant frequency
48. Continuous measurement of flow rates of dry granular fertilizer is done using
A) area-meters
B) velocity meters
C) anemometer
D) weighing meters
49. Pick out the symbol for “locally mounted instrument” in instrumentation diagram
50. The difference at any instant between the value of the controlled variable and the setpoint is called
A) differential gap
B) deviation
C) derivative time
D) error ratio
51. “A control system is unstable if the open-loop frequency response exhibits an amplitude ratio exceeding unity at the cross-over frequency.” This is
A) Routh stability criterion
B) Bode stability criterion
C) Nyquist criterion
D) both Nyquist criterion & Routh stability criterion
52. The resistance of a gas in a vessel is
53. A rotameter
A) is inaccurate for low flow rates
B) incurs constant but very large permanent pressure drop
C) incurs constant and small permanent pressure drop
D) need not be mounted always vertically
54. Conversion formula for converting amplitude ratio (AR) into decibels is
A) Decibel=20 log e(AR)
B) Decibel=20 log10 (AR)0.5
C) Decibel=20 log10 (AR)
D) Decibel = log10 (AR)
55. Which of the following relates the absorption and evolution of heat at the junctions of a thermocouple to the current flow in the circuit?
A) Seebeck effect
B) Peltier effect
C) Thomson effect
D) Joule heating effect
56. The dilatometer is used to measure
A) contraction/expansion due to changes in temperature
B) deflection
C) stress
D) strain
57. Hot wire anemometer is used for the measurement of
A) very high temperature
B) thermal conductivity of gases
C) flow rates of fluid
D) flow rates of granular solids
58. Starting temperature of optical radiation pyrometer is
A) 800°C
B) 1200°C
C) 1500°C
D) 400°C
59. In the case of flow measurement by an orifice, the pressure difference signal is proportional to
A) Q2
B) 1/√Q
C) Q3
D) Q
60. Radiation pyrometers
A) can not measure the temperature of objects without making physical contact
B) none of the answers
C) need not “see” the temperature source; it is measuring
D) have very low speed of response
61. A barometer measures
A) dynamic pressure
B) both absolute and gauge pressure
C) gauge pressure
D) absolute pressure
62. A controller action in which there is a continuous linear relation between the value of the controlled variable and rate of change of controlled output signal is called
A) derivative action
B) proportional action
C) proportional-integral action
D) integral action
63. Phase plane method is used for
A) both linear-behavior & non-linear behavior
B) linear-behavior
C) neither linear-behavior nor non-linear behavior
D) non-linear behavior
64. The fluid used in hydraulic controller is
A) water
B) air
C) steam
D) oil
65. Floating control action
A) both changes the position of the final control element from on to off & is used to counteract rapid load changes
B) changes the position of the final control element from on to off
C) is used to counteract rapid load changes
D) moves the final control element at constant speed in either direction in response to an error signal
66. Orifice plates for flow measurement
A) incurs very low permanent pressure loss
B) can’t be easily interchanged
C) is best for very large liquid flows and big pipelines
D) has poor accuracy on high orifice ratios (above 0.75)
67. What is the ratio of output amplitude to input amplitude for a sinusoidal forcing function in a first-order system?
A) 1
B) none of the answers
C) <1
D) >1
68. Bode diagram is a plot of
A) log (AR) vs. f and log Φ vs.
B) AR vs.log (f) and Φ vs. log (f)
C) log (AR) vs. log (f) and Φ vs. log (f)
D) log (AR) vs. log f
69. 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°
70. Which of the following shows maximum dip affect (indicating reverse direction of temperature change)?
A) bimetallic thermometer
B) mercury thermometer
C) thermocouple
D) radiation pyrometer
71. In Bode stability criterion, the amplitude ratio at 180° should be
A) 1
B) >1
C) 0
D) <1
72. For measuring the temperature of a furnace, which is the most suitable instrument?
A) Thermocouple
B) Platinum resistance thermometer
C) Optical pyrometer
D) Bimetallic thermometer
73. A negative gain margin expressed in decibels means
A) both a stable system & critically damped system
B) a stable system
C) unstable system
D) critically damped system
74. The time difference by which the output of a P-D controller leads the input when the input changes linearly with time is called
A) derivative time
B) error ratio
C) gain
D) proportional sensitivity
75. Thermocouples
A) has a very slow speed of response
B) can’t be connected to the measuring instrument remotely located
C) need cold junction compensation
D) are much less accurate compared to bimetallic or vapor pressure thermometer
76. Which of the following is suitable for measuring the temperature of a red hot moving object (e.g. steel ingots on roller table)?
A) thermocouple
B) radiation pyrometer
C) radiograph
D) thermistor
77. Regulator problem means that
A) both setpoint and load are constant
B) load is constant
C) set point is constant
D) neither set point nor load is constant
78. The gain margin is equal to the
A) reciprocal of amplitude ratio
B) amplitude ratio
C) gain in controller
D) gain in controller
79. The level of a liquid under pressure can be determined using
A) diaphragm box system
B) air-trap system
C) bubbler system
D) differential pressure manometer
80. The pitot tube is used
A) for highly accurate flow measurement
B) both for highly accurate flow measurement & when the line is large and the velocity is high
C) when the line is large and the velocity is high
D) when the fluid contains a lot of suspended material
81. Number of poles in a system with transfer function is
1 / ( S2 + 2S2 +1 )
A) 3
B) 2
C) 5
D) 1
82. Routh stability method uses
A) either Open loop transfer function or closed-loop transfer function
B) Open-loop transfer function
C) neither Open loop transfer function nor closed-loop transfer function
D) closed-loop transfer function
83. Which of the following is not a head flowmeter?
A) segmental orifice plate
B) pitot tube
C) rotameter
D) flow nozzle
84. Steady state deviation resulting from a change in the value of the load variable is
A) offset
B) deviation
C) static ratio
D) error ratio
85. A system with a transfer function 2s/(4s+1)
A) zero order
B) 1st order
C) 2nd order
D) 3rd order
86. Flow rate of sludge is measured by
A) Kennison nozzle
B) circular pipe
C) V-notch
D) rectangular notch
87. Which is the symbol for “pneumatic control valve”
88. Selection of material for thermocouple depends on the
A) minimum and maximum temperature
B) both depth of immersion in the hot fluid and minimum and maximum temperature
C) depth of immersion in the hot fluid
D) pressure and velocity condition of the fluid whose temperature is to be measured
89. Phase margin is equal to
A) phase lag + 180°
B) phase lag – 180°
C) 180° – phase lag
D) phase lag – 90°
90. Thermistor is a
A) semiconductor whose resistance decreases with temperature rise
B) metal whose resistance does not vary with temperature
C) metal whose resistance increases linearly with temperature rise
D) device for measuring nuclear radiation
91. In an area meter (e.g. rotameter), the flow rate is
A) inferred from the change in flow cross-section across which the pressure differential is zero
B) proportional to the square root of the differential pressure
C) all of the answers
D) inferred from the change in the area of an orifice in the flow line across which the pressure differential is constant zero
92. Composition of natural gas can be determined by
A) orsat apparatus
B) spectrometer
C) chromatograph
D) photometer
93. Instrumentation in a plant offers the advantage of
A) better quality of product
B) all of the answers
C) greater safety of operation
D) greater operation economy
94. Which of the following flow-metering instruments is an area meter?
A) rotameter
B) hot wire anemometer
C) pitot tube
D) venturi meter
95. Measurement of sub-zero Celsius temperature in the industry is done by
A) bi-metallic thermometer
B) resistance thermometers
C) gas thermometer
D) thermocouples
96. Pirani gauge is used for
A) measurement of very high pressure
B) liquid level under pressure
C) liquid level at atmospheric pressure
D) measurement of high vacuum
97. The response of a system to a sinusoidal input called
A) impulse response
B) step response
C) unit step response
D) frequency response
98. Which of the following factors does not influence measurement accuracy?
A) none of the answers
B) dead zone
C) reproducibility
D) static and dynamic error
99. Bellows are made of
A) thin copper
B) plastic
C) leather
D) paper
100. Which of the following controllers has maximum offset?
A) PI controller
B) P-controller
C) PD controller
D) PID controller
101. P-I controller as compared to P-controller has a
A) all of the answers
B) higher maximum deviation
C) longer response time
D) longer period of oscillation
102. Maximum differential pressure in liquid manometer is
A) 40 psi
B) 50 psi
C) 30 psi
D) 20 psi
103. Continuous measurement of moisture in paper is done by
A) hair-hygrometer
B) high resistance, Wheatstone’s bridge circuit
C) weighing
D) sling psychrometer
104. Phase lag of the first-order system is
A) tan-1 (ω)
B) 0
C) tan-1 (ωT)
D) π/2
105. The time required for the output of a first-order system to change from a given value to within 36.8% of the final value when a step change of input is made is/ called
A) setting time
B) rise time
C) time constant
D) derivative time
106. Example of a second-order instrument is a
A) bare mercury-glass thermometer
B) pressure gauge
C) Bourdon gauge
D) mercury-glass thermometer with covering
107. Servo problem means that
A) both setpoint is constant & load is constant
B) neither setpoint is constant nor load is constant
C) setpoint is constant
D) load is constant
108. Continuous measurement of moisture content of paper in paper industry is done by measuring
A) both electrical resistance through the paper & magnetic susceptibility
B) thermal conductivity through the paper
C) magnetic susceptibility
D) electrical resistance through the paper
109. Stroboscope is used for the measurement of
A) liquid level under pressure
B) depression of freezing point
C) frequency of light
D) rpm of a flywheel
110. Which thermocouple can be used to measure the temperature around 1400 °C?
A) copper-aluminum
B) copper-constantan
C) platinum-platinum+rhodium
D) aluminum-chromel
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