Types of Oscilloscope MCQ || Types of cathode Ray Oscilloscope Questions and Answers

11. A continuous sweep CRO uses a ______  as a time base generator.

  1. BJT
  2. UJT
  3. FET
  4. JFET

Answer.2. UJT

Explanation: 

A continuous sweep CRO using a UJT as a time base generator.  The UJT is used to produce the sweep.

 

12. The power supply generated in CRO is

  1. High voltage only
  2. Low Voltage only
  3. Both High and low voltage
  4. Medium voltage

Answer.3. Both High and low voltage

Explanation: 

Power Supply in CRO

There are two power supplies Generated in CRO

  1. Negative High Voltage (HV) supply
  2. Positive Low Voltage (LV) supply

The +ve volt supply is from + 300 to 400 V.

The -ve high voltage supply is from – 1000 to – 1500 V.

This voltage is passed through a bleeder resistor at a few mA. The intermediate voltages are obtained from the bleeder resistor for intensity, focus and positioning controls.

 

13. What are the advantages of Negative High Voltage (HV) supply in CRO

  1. Shock Protection
  2. No need of coupling Capacitor
  3. Less insulation is Needed
  4. All of the above

Answer.4. All of the above

Explanation: 

Advantages of using -ve HV Supply

(i) The accelerating anodes and the deflection plates are close to ground potential. The ground potential protects the operator from HV shocks when making connections to the plates.

(ii) The deflection voltages are measured wrt ground, therefore HV blocking or coupling capacitors are not needed, but low voltage rating capacitors can be used for connecting the HV supply to the vertical and horizontal amplifiers.

(iii) Less insulation is needed between positioning controls and chassis.

 

14. To display voice or music signal _____ is used in CRO.

  1. Triggered Sweep
  2. Continuous Sweep
  3. Frequency Sweep
  4. Any of the above

Answer.2. Continuous Sweep

Explanation: 

The continuous sweep is of limited use in displaying periodic signals of constant frequency and amplitude. When attempting to display voice or music signals, the pattern falls in and out of sync as the frequency and amplitude of the music vary resulting in an unstable display.

A triggered sweep can display such signals, and those of short duration, e.g. narrow pulses. In triggered mode, the input signal is used to generate substantial pulses that trigger the sweep. Thus ensuring that the sweep is always in step with the signal that drives it.

 

15. ______ used in CRO so that the input signal and the sweep frequency can be synchronized

  1. Time Sweep
  2. Phase Inverter
  3. Attenuator
  4. Triggered Circuit

Answer.4. Triggered Circuit

Explanation: 

  •  Trigger Circuit is used to convert the incoming signal into trigger pulses so that the input signal and the sweep frequency can be synchronized.
  • The trigger circuit is activated by signals of a variety of shapes and amplitudes, which are converted to trigger pulses of uniform amplitude for the precision sweep operation.
  • If the trigger level is set too low, the trigger generator will not operate.
  • On the other hand, if the level is too high, the UJT may conduct for too long and part of the leading edge of the input signal may be lost.

 

16. The dual-slope oscilloscope is needed to _________

  1. Compare more than two voltages
  2. Measure the voltage
  3. Measure the current
  4. Measure the time

Answer.1. Compare more than two voltages

Explanation:

  • The dual-trace oscilloscope has one cathode ray gun with an electronic switch, which switches two signals to a single vertical amplifier.
  • Sometimes it is necessary to compare the two or more voltage waveforms to analyze the electronic circuits and systems. It can be done by using two or more oscilloscopes but it is difficult to trigger the sweep of each oscilloscope precisely at the same time. This problem is solved by the use of dual trace or multitrace oscilloscopes.
  • In this method, the same electron beam is used to generate two traces that can be deflected from two independent vertical sources.

 

17. Which technique of a Dual Trace Oscilloscope maintains the phase between the signals?

  1. Analog mode
  2. Mixed mode
  3. Chop mode
  4. Alternate mode

Answer.2. Alternate mode

Explanation: 

  • The dual-trace oscilloscope has one cathode ray gun with an electronic switch, which switches two signals to a single vertical amplifier.
  • The dual-trace oscilloscope has one cathode ray gun with an electronic switch, which switches two signals to a single vertical amplifier.
  • To display two waveforms, the single beam must somehow be shared between the two traces.
  • Dual trace oscilloscopes almost invariably offer a front panel selectable choice of alternate and chopped modes as well as between traces.

 

18. What is the problem with using more than one oscilloscope?

  1. Measuring the signal’s parameters
  2. Triggering
  3. Supply voltage
  4. Errors in reading

Answer.2. Triggering

Explanation: 

  • Sometimes it is necessary to compare the two or more voltage waveforms to analyze the electronic circuits and systems. It can be done by using two or more oscilloscopes but it is difficult to trigger the sweep of each oscilloscope precisely at the same time. This problem is solved by the use of dual trace or multitrace oscilloscopes.
  • In this method, the same electron beam is used to generate two traces that can be deflected from two independent vertical sources.

 

19.  Electronic switch in Dual trace oscilloscope is controlled by _________

  1. D flip-flop
  2. SR flip-flop
  3. T flip-flop
  4. JK flip-flop

Answer.3. T flip-flop

Explanation: 

In a Dual trace Oscilloscope, there are two separate vertical input channels A and B. A separate preamplifier and attenuator stage exists for each channel. Hence amplitude of each input can be individually controlled. After the preamplifier stage, both the signals are fed to an electronic switch. The switch has the ability to pass one channel at a time via delay line to the vertical amplifier.

Dual-trace-CRO

An electronic switch is controlled by using a toggle flip-flop. The switching takes place at the start of each new sweep. The switching rate of an electronic switch is synchronized to the sweep rate so that CRT spot traces channel A signal on one sweep and channel B signal on the next succeeding sweep.

Thus two-channel are alternately connected to the vertical amplifier. The change over of an electronic switch takes place during the flyback period of the sweep.

 

20. Independent traces can be obtained using ____________

  1. 4 methods
  2. 6 methods
  3. 2 methods
  4. 8 methods

Answer.3. 2 methods

Explanation: 

  1. The comparison of two or more voltages is very much necessary in the analysis and study of many electronic circuits and systems.
  2. This is possible by using more than one oscilloscope but in such a case it is difficult to trigger the sweep of each oscilloscope precisely at the same time.
  3. A common and less costly method to solve this problem is to use dual-trace or multitrace oscilloscopes.
  4. In this method, the same electron beam is used to generate two traces that can be deflected from two independent vertical sources.
  5. The two methods are used to generate two independent traces which are the alternate sweep method and other is chop method.

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