Process Control and Instrumentation

181. Starting temperature of optical radiation pyrometer is _________ °C.

1. 800
2. 400
3. 1200
4. 1500

View answer

182. Strain gage pressure transducers are used to measure _________ pressures.

1. Gage as well as vacuum
2. Absolute as well as differential
3. Both (A) and (B)
4. Neither (A) nor (B)

View answer

183. Strain gage uses an electrical conductor wire, which when elastically stretched increases in length and reduces in diameter. Both these dimensional changes result in _________ in the electrical resistance of the wire.

1. No change
2. Decrease
3. Increase
4. Exponential decrease

View answer

184. Stroboscope is used for the measurement of

1. Rpm of a flywheel
2. Frequency of light
3. Depression of freezing point
4. Liquid level under pressure

View answer

185. Sub-zero temperature (<0°C) can be measured by a constant volume gas thermometer employing

1. Helium
2. Nitrogen
3. Hydrogen
4. None of these

View answer

186. Suppose that the gain, time constant and dead time of a process with the following transfer function: G_c(s) = 10 exp( - 0.1s)/(0.5s + 1) are known with a possible error of ± 20% of their values. The largest permissible gain K_c of a proportional controller needs to be calculated below taking the values of process gain, time constant and dead time as

1. 8, 0.6, 0.08
2. 12, 0.6, 0.12
3. 8, 0.6, 0.12
4. 12, 0.4, 0.08

View answer

187. Temperature control of an exothermic chemical reaction taking place in a CSTR is done with the help of cooling water flowing in a jacket around the reactor. The types of valve and controller action to be recommended are

1. Air to open valve with the controller direct acting
2. Air to close valve with the controller indirect acting
3. Air to open valve with the controller indirect acting
4. Air to close valve with the controller direct acting

View answer

188. Temperature measurement by optical pyrometer is done above _________ point, which is 1063°C.

1. Antimony
2. Gold
3. Silver
4. Nickel

View answer

189. Temperature measurement range of iron-constantan thermocouple is 0 to 870°C. It can be used to measure sub zero temperature, because at lower temperature

1. Emf produced is very low of the order of microvolt
2. Embrittlement of iron occurs
3. Rusting of iron takes place
4. Both (B) and (C)

View answer

190. Temperature measuring instruments are standardised mostly with _________ points of pure substances.

1. Melting
2. Boiling
3. Both (A) & (B)
4. Neither (A) nor (B)

View answer