A negative gain margin expressed in decibels means a/an ____________ system?

Related Mcqs:

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

   A. 8, 0.6, 0.08
   B. 12, 0.6, 0.12
   C. 8, 0.6, 0.12
   D. 12, 0.4, 0.08

2. Typical specifications for design stipulates the gain margin and phase margin to be respectively__________________?

   A. > 1.7 and > 30°
   B. 30°
   C. < 1.7 and 1.7 and < 30°

3. Conversion formula for converting amplitude ratio (AR) into decibels is ________________?

   A. Decibel = 20 log10 (AR)
   B. Decibel = 20 loge (AR)
   C. Decibel = 20 log10 (AR)0.5
   D. Decibel = 20 loge (AR)0.5

4. An amplitude ratio of 0.1 corresponds to _____________ decibels?

   A. 20
   B. -20
   C. 10
   D. -10

5. Gain margin is equal to the_________________?

   A. Amplitude ratio
   B. Reciprocal of amplitude ratio
   C. Gain in P controller
   D. Gain in P-I controller

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

   A. 0.0001
   B. 0.001
   C. 0.01
   D. 0.1

7. 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 ?

   A. e-ηS
   B. (T1S + 1)/(T2S + 1)
   C. (T1S/(T2S + 1)
   D. (T1S + 1)/(T2S

8. Find the ultimate gain and frequency for a proportional controller in the case of a process having the transfer function Gp(s) = 1/(4s + 1)(2s + 1)(s + 1) ?

   A. w = 1/√14, Kc = 45/7 √14
   B. w = √(7/6), Kc = 46/3
   C. w = 1, Kc = 13
   D. w = √(7/8), Kc = 45/4

9. A proportional controller with a gain of Kc is used to control a first order process. The offset will increase, if________________?

   A. Kc is reduced
   B. Kc is increased
   C. Integral control action is introduced
   D. Derivative control action is introduced

10. A first order system with unity gain and time constant η is subjected to a sinusoidal input of frequency w = 1/η. The amplitude ratio for this system is______________?

    A. 1
    B. 0.5
    C. 1/√2
    D. 0.25