Process Control and Instrumentation

201. The deflection in diaphragm (which is used as pressure sensor in pneumatic and electronic instruments) is dependent on the metal thickness, its diameter (D) and shape & number of corrugations. Its deflection is proportional to

  1. d
  2. d2
  3. d3
  4. d4

Correct answer: (D)
d4

202. The deflection of the free end of the bimetallic strips in a bimetallic thermometer with temperature is nearly

  1. Linear
  2. Non-linear
  3. Parabolic
  4. Hyperbolic

Correct answer: (A)
Linear

203. The fluid used in hydraulic controller is

  1. Water
  2. Steam
  3. Air
  4. Oil

Correct answer: (D)
Oil

204. The frequency at which maximum amplitude ratio is attained is called the _________ frequency.

  1. Corner
  2. Resonant
  3. Cross-over
  4. Natural

Correct answer: (B)
Resonant

205. The frequency response of a dynamic element shows a constant magnitude ratio at all frequencies. The element exhibits a negative phase shift at all frequencies. The absolute value of the phase shift increases linearly with frequency. The element has the transfer function

  1. e-ηS
  2. (T1S + 1)/(T2S + 1)
  3. (T1S/(T2S + 1)
  4. (T1S + 1)/(T2S

Correct answer: (A)
e-ηS

206. The frequency response of a first order system, has a phase shift with lower and upper bounds given by

  1. - ∞, π/2
  2. -π/2, π/2
  3. -π/2, 0
  4. 0, π/2

Correct answer: (D)
0, π/2

207. The function of a transducer is to

  1. Modify the input signal
  2. Amplify the input signal
  3. Convert the primary signal into a more useful quantity, usually an electric impulse
  4. Codify/decodify the input signal

Correct answer: (C)
Convert the primary signal into a more useful quantity, usually an electric impulse

208. The initial value (t = 0) of the unit step response of the transfer function [(s + 1)/(2s + 1)] is

  1. 0
  2. ½
  3. 1
  4. 2

Correct answer: (B)
½

209. The inverse Laplace transform of the function f(S) = 1/S (1 + S) is

  1. 1 + et
  2. 1 - et
  3. 1 + e-t
  4. 1 - e-t

Correct answer: (D)
1 - e-t

210. The Laplace transform of exp(at), where a < 0, is defined only for the Laplace parameter, s > a since

  1. The function is exponential
  2. The Laplace transform of integral of exp(at) has finite values only for s < a
  3. The Laplace transform integral of exp(at) has initial values only for s < a
  4. The function exp(at) is piece-wise continuous only for s < a

Correct answer: (B)
The Laplace transform of integral of exp(at) has finite values only for s < a

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