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2-20. Which of the following devices are
magnetic error detectors?
1. CXs
2. E-transformers
3. Summing networks
4. All of the above
2-21. A dc rate generator is used in which of
the following loops of a velocity servo
system?
1. Prime mover
2. Feedback
3. Control
4. Error
2-22. What is the function of a modulator in a
servo system?
1. To change the frequency of an ac
error signal
2. To impress an ac error signal on an ac
carrier
3. To convert a dc error signal to an ac
error signal
4. To convert an ac error signal to a dc
error signal
2-23. In a servo system that uses a modulator,
what characteristic of the modulator
output determines the direction of load
movement?
1. Amplitude
2. Frequency
3. Polarity
4. Phase
2-24. What phase relationships between the
input and reference signals are sensed by
a servo demodulator?
1.
0º and 180º
2.
45º and 225º
3.
90º and 270º
4. 135º and 315º
2-25. In a properly operating servo system,
what is the phase relationship between
the reference voltages to the error
detector and the demodulator?
1. In phase only
2. 180º out of phase only
3. Out of phase; somewhere between 0º
and 180º
4. In phase or 180º out of phase,
depending on the demodulator input
2-26. Which of the following should be a
characteristic of a servo amplifier?
1. Narrow frequency band
2. High output impedance
3. 180º phase shift
4. Low noise level
2-27. An ac servo motor would probably be
used instead of a dc servo motor in which
of the following situations?
1. To move heavy loads at a constant
speed
2. To move heavy loads at variable
speeds
3. To move light loads at a constant
speed
4. To move light loads at variable
speeds
2-28. Which of the following circuits that is
required in a multispeed servo system is
NOT required in a single-speed servo
system?
1. Position sensor
2. Error detector
3. Feedback loop
4. Synchronizer
