Cathode Ray Oscilloscope MCQ || Cathode Ray Oscilloscope Questions and Answers

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.

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.

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.

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.

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.

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.

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.

Answer.2. Vertical and horizontal

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.

The X-Y mode means the oscilloscope operates from A as the vertical signal and channel B as the horizontal signal. Thus in this mode very accurate X-Y measurements can be done.

Answer.2. 2

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.

The X-Y mode means the oscilloscope operates from A as the vertical signal and channel B as the horizontal signal. Thus in this mode very accurate X-Y measurements can be done.

In a Dual Trace Oscilloscope, two vertical inputs exist. The two channels are known as A and B.  Depending on the selection of front panel controls several modes of operation can be selected such as channel A only, channel B only, channel A and B as separate trace, signals A+ B, A-B, B—A or (A + as a single trace.

Answer.1. An electronic switch

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.

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.

Answer.1. Flyback Period

Explanation: 

The change over of an electronic switch takes place during the flyback period of the sweep. During the flyback, the electron beam is invisible and the change over is also invisible i.e. without flicker. Thus the alternate mode displays one vertical channel for a full sweep and the next vertical channel for the next sweep.

Answer.3. Both 1 and 2

Explanation: 

The main limitation of the alternate mode method in dual trace CRO is that the display is not the actual representation of two events taking place simultaneously. The signals are displayed as if they were existing at two different times.

Similarly, the alternate mode cannot be used for displaying very low-frequency signals.

Answer.3. Chop Mode

Explanation: 

In Chop mode there is a switching from one vertical channel to other, many times during a single sweep. This switching from one vertical channel to other is at such a rapid rate that the display is created from small segments of the actual waveform.

The electronic switch is free running oscillator at a rate of 100 to 500 kHz independent of the sweep generator frequency. Thus the switch successively connects the small segments of the channel A and B waveforms to the main amplifier.

Answer.4. All of the above

Explanation: 

The front panel control of dual trace oscilloscope can be divided into four major groups

1. Control Group
2. Horizontal Group
3. Vertical Group
4. Trigger Group

( Control Group: This group includes the following controls:

(i) Focus: This controls the size of the electron beam spot on the screen.

(ii) Trace rotation: Due to external fields or internal disturbance, if the trace is not horizontal then using the screwdriver adjustment beam can be made horizontal.

(iii) Calibration: It provides a standard signal to calibrate the vertical amplifier control. In most CROs, it is a square wave of 1 V peak to peak.

(iv) Intensity: It is generally the part of on/off control and brightness of the CRT that can be controlled using this control.

(v) Power on/off: The power to the device can be turned on or off using this control.

( Horizontal Group: This group includes the following control:

(i) Horizontal position: It moves the trace left and right on the screen.

(ii) Sweep mode: The sweep mode control selects the various modes such as automatic (AUTO), normal (NORM), and single sweep (SINGLE).

(iii) Sweep time: It is the main horizontal timing control. The time per division required to sweep the beam from left to right on the CRT screen can be determined using this control.

Answer.1. 2 beams

Explanation: 

The two beams could be produced by two independent electron gun assemblies, or by a single gun and a splitter plate to slice the beam in half. An oscilloscope using this type of dual-trace operation is known as a dual-beam oscilloscope.

The dual-beam CRO uses two complete separate electron beams. The dual-beam analog oscilloscope can display two signals simultaneously. A special dual-beam CRT generates and deflects two separate beams.

Answer.2. Two electron guns

Explanation: 

The two beams could be produced by two independent electron gun assemblies, or by a single gun and a splitter plate to slice the beam in half. An oscilloscope using this type of dual-trace operation is known as a dual-beam oscilloscope.

The dual-beam CRO uses two complete separate electron beams. The dual-beam analog oscilloscope can display two signals simultaneously. A special dual-beam CRT generates and deflects two separate beams

Answer.2. 2 vertical deflection plates

Explanation: 

• In dual-beam oscilloscopes, there are two vertical input signals.
• In a dual-beam oscilloscope, a specially designed C.R.T. is used which is capable of producing two completely distinct electron beams so that they can be deflected independently in the vertical plane.
• In the split beam technique, the single electron gun is split into two distinct beams mechanically. While in other techniques, two separate electron guns are used which produce their own beam.
• Thus in dual beam, C.R.T. two sets of vertical deflection plates are used, one set for each channel but only one set of horizontal deflection plates. The simplified block diagram of dual-beam C.R.O.

Answer.4. Channel A or B

Explanation: 

• The dual-beam oscilloscope has two vertical deflection plates and two separate channels A and B for the two separate input signals.
• Each channel consists of a preamplifier and an attenuator. A delay line, main vertical amplifier, and a set of vertical deflection plates together form a single channel.
• There is a single set of horizontal plates and a single time base circuit.
• The horizontal deflection system consists of a sweep generator that drives a single set of horizontal deflection plates in the C.R.T. and sweeps both the vertical signals across the C.R.T. screen at the same rate.
• The sweep generator can be triggered internally by the channel A signal or channel B signal.
• As regards triggering of the sweep generator it can be done internally from either of channel or by the externally applied trigger or it can be triggered from the line voltage.

Answer.2. Both 1 and 2

Explanation: 

The dual-beam oscilloscope can generate the two-electron beams within the cathode ray tube either by using a double electron gun tube or by splitting beam. In this method, the brightness and focus of each beam are controlled separately. But two tubes increase the size and weight of the oscilloscope and it looks bulky.

Answer.2. Sweep Generator

Explanation: 

The horizontal deflection of the dual-beam oscilloscope system consists of a sweep generator that drives a single set of horizontal deflection plates in the C.R.T. and sweeps both the vertical signals across the C.R.T. screen at the same rate. As regards triggering of the sweep generator it can be done internally from either of channel or by an externally applied trigger or it can be triggered from the line voltage.

Answer.4. All of the above

Explanation: 

The dual-beam oscilloscopes are widely used and are more versatile than the single beam type. They have the advantage that two waveforms can be displayed simultaneously. This enables
waveforms to be compared, in terms of their amplitudes, shape, phase angle, or frequency.