51. During temperature changing conditions, quite appreciable difference, occurs be tween the -true-temperature and the measured temperature because of the time required for the transfer of heat through thermometer pockets (thermowells) to thermometer sensing element. This time lag is of the order of :
(a) 0.1 to 1 sec
(b) 1 to 2.5 sec
(c) 2.5 to 10 or 20 sec
(d) 25 to 100 sec
(e) 100 to 500 sec.
Ans: c
52. Pick up false statement:
(a) copper-constantan thermocouple is a stable couple resistant to both oxidis¬ing and reducing atmosphere, but needs protection from acidic vapours
(b) Iron-constantan thermocouple suffers from oxidation attack on iron wire, if exposed
(c) iron-constantant couple can be made stable by using enamelled iron
(d) Both wires of chromel-alumel ther-mocouples are prone to damage by sulphurous gases
(e) copper-constantan thermocouple is used as a reference standard for calibration purposes.
Ans: e
53. Automatic cold junction compensation in thermocouple is provided by :
(a) connecting thermocouple wires, in op-position
(b) a nickel wire resistance in series with a manganin resistance
(c) maintaining cold junction temperature constant by a cooling unit
(d) using a photovoltaic cell
(e) connecting a dry battery cell in opposi¬tion.
Ans: b
54. The material used for resistance temperature sensor is :
(a) copper
(b) nickel
(c) platinum
(d) any one of above
(e) none of above.
Ans: d
55. To prevent self-heating errors becoming too great, the current through platinum element (100 ohm) is kept at a very small value :
(a) 0.1 raA
(b) 1 mA
(c) 5 mA
(d) 20 mA
(e) 50 mA.
Ans: c
56. In calibration of temperature sensors by fixed point method, the device is calibrated at:
(a) ice point (0°C)
(b) steam point (100°C)
(c) sulphur point (444.6°C)
(d) all of the above
(e) none of the above.
Ans: d
57. Pick up correct statement about calibration of temperature sensors by comparison method using liquid bath :
(a) water is used for temperatures from 0 to I00°C
(b) special grade of paraffin oil is used for temperatures between 100 and 200°C
(c) For temperature between 200 and 600°C, a mixture of sodium nitrate and potassium nitrate is used
(d) all of above are true
(e) none of above is true.
Ans: d
58. Local velocity is measured by a :
(a) pitot tube
(b) venturi tube
(c) orifice plate
(d) vena contracta device
(e) nozzle.
Ans: a
59. Flange taps in case of orifice plate are installed :
(a) 25 mm from each side of the orfice plate
(b) D (pipe diameter) upstream and D/2 downstream
(c) just at surface of orifice plate
(d) 2.5 D upstream and 8 D downstream
(e) any one of the above.
Ans: a
60. Vena-contracta taps are employed :
(a) D upstream and D downstream from the plate
(b) D upstream and at vena contracta
(c) 2 D upstream and at vena contracta
(d) just at surface of plate upstream and at vena contracta
(e) any one of the above.
Ans: b
Read More Questions:
Process Instrumentation and Control - Mechanical Engineering MCQs Part1
Process Instrumentation and Control - Mechanical Engineering MCQs Part2
(a) 0.1 to 1 sec
(b) 1 to 2.5 sec
(c) 2.5 to 10 or 20 sec
(d) 25 to 100 sec
(e) 100 to 500 sec.
Ans: c
52. Pick up false statement:
(a) copper-constantan thermocouple is a stable couple resistant to both oxidis¬ing and reducing atmosphere, but needs protection from acidic vapours
(b) Iron-constantan thermocouple suffers from oxidation attack on iron wire, if exposed
(c) iron-constantant couple can be made stable by using enamelled iron
(d) Both wires of chromel-alumel ther-mocouples are prone to damage by sulphurous gases
(e) copper-constantan thermocouple is used as a reference standard for calibration purposes.
Ans: e
53. Automatic cold junction compensation in thermocouple is provided by :
(a) connecting thermocouple wires, in op-position
(b) a nickel wire resistance in series with a manganin resistance
(c) maintaining cold junction temperature constant by a cooling unit
(d) using a photovoltaic cell
(e) connecting a dry battery cell in opposi¬tion.
Ans: b
54. The material used for resistance temperature sensor is :
(a) copper
(b) nickel
(c) platinum
(d) any one of above
(e) none of above.
Ans: d
55. To prevent self-heating errors becoming too great, the current through platinum element (100 ohm) is kept at a very small value :
(a) 0.1 raA
(b) 1 mA
(c) 5 mA
(d) 20 mA
(e) 50 mA.
Ans: c
56. In calibration of temperature sensors by fixed point method, the device is calibrated at:
(a) ice point (0°C)
(b) steam point (100°C)
(c) sulphur point (444.6°C)
(d) all of the above
(e) none of the above.
Ans: d
57. Pick up correct statement about calibration of temperature sensors by comparison method using liquid bath :
(a) water is used for temperatures from 0 to I00°C
(b) special grade of paraffin oil is used for temperatures between 100 and 200°C
(c) For temperature between 200 and 600°C, a mixture of sodium nitrate and potassium nitrate is used
(d) all of above are true
(e) none of above is true.
Ans: d
58. Local velocity is measured by a :
(a) pitot tube
(b) venturi tube
(c) orifice plate
(d) vena contracta device
(e) nozzle.
Ans: a
59. Flange taps in case of orifice plate are installed :
(a) 25 mm from each side of the orfice plate
(b) D (pipe diameter) upstream and D/2 downstream
(c) just at surface of orifice plate
(d) 2.5 D upstream and 8 D downstream
(e) any one of the above.
Ans: a
60. Vena-contracta taps are employed :
(a) D upstream and D downstream from the plate
(b) D upstream and at vena contracta
(c) 2 D upstream and at vena contracta
(d) just at surface of plate upstream and at vena contracta
(e) any one of the above.
Ans: b
Read More Questions:
Process Instrumentation and Control - Mechanical Engineering MCQs Part1
Process Instrumentation and Control - Mechanical Engineering MCQs Part2
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