Process Control and Instrumentation

221. The second order system with the transfer function 4/(S² + 2s + 4) has a damping ratio of

1. 2
2. 0.5
3. 1
4. 4

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222. The temperature of tempering oil baths maintained at 400°C during heat treatment of steel is measured by a/an _________ thermocouple.

1. Chromel-alumel
2. Iron-constantan
3. Platinum-platinum/rhodium
4. None of these

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223. The temperature range for which copper resistance thermometer can be used is _________ °C.

1. 0 to 150
2. -200 to 150
3. 350 to 750
4. 500 to 900

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224. The term analogous to the electrical current in a thermal system is the

1. Temperature difference
2. Heat flow rate
3. Heat content in the system
4. None of these

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225. The term analogous to voltage in a single tank system is the

1. Heat content of the system
2. Liquid volume in the tank
3. Flow rate
4. Level of liquid

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226. The thermal emf-temperature relationship of most thermocouples is

1. Linear
2. Parabolic
3. Exponential
4. Square root

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227. The time constant of a first order process with resistance R and capacitance C is

1. R + C
2. R - C
3. RC
4. 1/RC

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228. The time constant of a unity gain, first order plus time delay process is 5 min. If the phase lag at a frequency of 0.2 rad/min is 60°, then the dead time (in minutes) is

1. 5π/12
2. π/6
3. π/12
4. π/3

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229. The transfer function for a P-D controller is

1. K_c(1+ηD s)
2. K_c(1 +1/ηD s)
3. K_c ηD s
4. K_c/ηD s

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230. The transfer function for a PID controller is (where, η i is the integral (reset) time and ηD is the derivative time.)

1. K_c(1 + η_is + η_D ). s
2. K_c[1 + (1/η_is) + η_D . s)
3. K_c(1 + η_is + (1/η_D . s)
4. None of these

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