Process Control and Instrumentation

251. Thermodynamic Celsius scale of temperature measurement is

1. Defined on the basis of melting point of ice and evaporation temperature of water vapor
2. Defined on the basis of melting point of ice and condensation temperature of water vapor
3. Having an interval of 100° between ice point to steam point
4. Both (B) and (C)

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252. Time constant is the

1. Time taken by the controlled variable to reach 63.2% of its full change
2. Same as transportation lag
3. Same as dead time
4. Time required by the measured variable to reach 63.2% of its ultimate change

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253. To increase the speed of response of a pressure spring liquid or gas expansion thermometer, the clearance space between the thermometer bulb and the thermal well should not be filled with

1. Air
2. A metal powder or graphite
3. Oil
4. Mercury

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254. Transfer function of transportation lag is

1. e^TS
2. e^-TS
3. 1/(Ts + 1)
4. None of these

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255. Turbine flow meters are suitable for

1. Very limited flow ranges
2. Cryogenic flow measurements
3. Aerospace and in air borne applications
4. Both (B) and (C)

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

1. < 1.7 and < 30°
2. < 1.7 and < 30°
3. < 1.7 and < 30°
4. < 1.7 and < 30°

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257. Use of I-control along with P-control facilitates

1. Elimination of offset
2. Reduction of offset
3. Reduction of stability time
4. None of these

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258. Vapour actuated pressure spring thermometer does not require ambient temperature compensation. Ambient temperature compensation is provided in gas or liquid expansion pressure spring thermometer by

1. Making the volume of thermometer bulb as large as conveniently possible
2. Reducing the volume of the capillary to a minimum
3. Reducing the volume of the receiving element to a minimum
4. All 'a', 'b' & 'c'

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259. Very low pressure is expressed in microns (μ), which is equal to _________ mm of Hg column (absolute) at 0°C.

1. 0.0001
2. 0.001
3. 0.01
4. 0.1

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260. Volumetric expansion is the working principle of the _________ thermometers.

1. Mercury in glass
2. Constant volume gas
3. Vapor pressure
4. Bimetallic

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