# Front Panel Controls of CRO MCQ || Front Panel Controls of CRO Questions and Answers

1. Front panel of a CRO has ______

1. 4 sections
2. 8 sections
3. 15 sections
4. 20 sections

Explanation:

The front panel of a CRO has 4 sections

1. Basic controls
2. Vertical section
3. Horizontal section
4. Z-axis intensity control

Basic Control:- The basic control in CRO consists of

1. On-off knob
2. Intensity or Brightness
3. Focus
4. Focus Control
5. Scale Illumination

Horizontal Section Consist of four parts

1. Position Knob
2. Timebase control
3. Sweep selector switch
4. Synchronization

The measure part of the vertical section is

1. Vertical Scale
2. Invert
3. Position
4. X10 knob
5. Vertical coupling Switch
6. Vertical Mode Control

2. ______ is used to shift the inputs in CRO.

1. Position Knob
2. X10 Knob
3. Alternate Knob
4. Any of the above

Explanation:

In a Cathode Ray Oscilloscope, the alternate knob is used to transition between the two different input signals.

Input A is displayed first, then input B is displayed, then input Aagainand soon by using the vertical position control, the two traces can be separated vertically, and thus, relations between the two signals can be studied.

3. What is the role of the intensity section in a CRO?

1. Decreases the light intensity
2. Controls light intensity
3. Increases the light intensity
4. Keeps the light intensity zero

Explanation:

Intensity or Brightness: The intensity section in a CRO controls the intensity or brightness of the light produced by the beam spot.

• It actually controls the number of electrons per second that are bombarding the screen which determines the brightness of the spot.
• In general, the spot should be no brighter than it needs to be since high-intensity spots shorten the life of the cathode ray tube.
• Also allowing the bright spot to stand still for a long time at the same position on the screen, can burn off the phosphor on the tube and produce a dead spot on the screen at that point.

4. Position knob in a CRO indicates ________

1. Voltage position only
2. Time position only
3. Current position only
4. Any pattern’s position

Explanation:

Position Knob: In a CRO the position knob is used for indicating the position of any pattern on the screen. The position knob is used to shift the display as a whole to left or right.

There are two knobs — one for controlling the horizontal position and another for controlling the vertical position. The spot can be moved to left or right i.e. horizontally with the help of a knob, which regulates the dc potential applied to the horizontal deflection plates, in addition to the usual sawtooth-wave.

5. What is the role of the focus section in a CRO?

1. Increases the focus
2. Decreases the focus
3. Controls sharpness
4. Maintains the focus zero

Explanation:

Focus: The focus section in a CRO controls the sharpness of the spot. A sharper spot is always preferred. The focusing of the spot is also obtained by varying the voltage applied to the focusing anodes of the cathode ray tube.

Focus Control: It is also known as Astigmatism. This is another focus control. With the help of focus control and astigmatism control, a very sharp spot can be obtained both in the center and also at the edges of the screen.

6. X10 in a CRO means ______

1. One-tenth
2. Control knob
3. 10 times as normal
4. Attenuate the voltage by 10 times

Explanation:

X10 in a CRO means Control knob.

X10 Knob: This control makes the gain of the vertical amplifier 10 times as great as normal, it changes the scale factor by a factor of 10. Thus if the X 10 switch turned ‘ON” and the scope is set to 0.05 V/cm, if the actual scale factor is 0.005 V/cm, if the actual scale factor is 0.005 V/ cm or 5 mV/em.

7. What is the role of astigmatism in a CRO?

1. Increases the intensity
2. Used for voltage stability
3. Diminishes the intensity
4. Focus control

Explanation:

The role of astigmatism in a CRO is Focus control.

Focus Control: It is also known as Astigmatism. This is another focus control. With the help of focus control and astigmatism control, a very sharp spot can be obtained both in the center and also at the edges of the screen.

8. What is the role of an invert in a CRO?

1. Inverts the output
2. Inverts the input
3. Attenuates the input
4. Magnifies the input

Explanation:

Invert in a CRO control inverts the input signal; That is, it multiplies it by-1. Then positive input voltages become negative and cause downward deflections.

9. What is the role of scale illumination in a CRO?

1. Measurement
2. Illumination
3. Sharpness
4. Stability

Explanation:

The role of scale illumination in a CRO is used for measurement.

• Most of the C.R.O have some sort of plastic screen in front of the cathode ray tube.
• This screen has a grid engraved on it, giving it an appearance similar to that of graph paper. This is called graticule.
• This scale facilitates the measurement of the oscilloscope.
• The scale illumination control illuminates the scale and hence the lines on the scale can be seen very easily.
• The electrons striking the screen are either repelled back or cause the secondary emission of electrons.
• The secondary electron affects the display on the screen.
• Hence to collect such electrons, a conductive coating is deposited inside the surface of CRT, except the screen.

10. The time base control in CRO is calibrated in terms of ______

1. Time per meter
2. Time per centimeter
3. Meter per second
4. Division per time

Explanation:

Time Base Control: The oscilloscope is usually used to observe the waveform of time-varying signals. Most of the horizontal section of the scope is devoted to generating a time base for such signals. The time base control is calibrated in terms of time per centimeter or time per division.

11. When the sweep selectors switch is in _____ position, the horizontal amplifier receives an input from the sawtooth sweep generator.

1. Vertical Position
2. Horizontal Position
3. Linear Position
4. Any of the above

Explanation:

Sweep Selector Switch: When the sweep selectors switch S, is in a linear position, the horizontal amplifier receives an input from the sawtooth sweep generator which is triggered by the synchronous amplifier.

12. The function of synchronization switch in CRO is _____

1. To obtain vertical pattern
2. To obtain horizontal pattern
3. To obtain stationary pattern
4. All of the above

Explanation:

Synchronization: To obtain the stationary pattern on the screen, synchronization is used.

It is used to operate the time base generator such that the frequency of sawtooth voltage is an integral multiple of input signal frequency.

There are various signals which can be applied to the trigger circuit. The signals can be selected using a synchronous selector switch.

13. The choice of vertical coupling switch in CRO is _____

1. AC
2. DC
3. Ground
4. All of the above

Explanation:

Vertical Coupling Switches: This switch controls the coupling to the vertical amplifier. The usual choice is AC, DC or ground. The meaning of these various positions are as follows:

(i) DC: The vertical amplifier had dc coupling throughout so that the deflection corresponds to both the ac and the dc components of the input.

(ii) AC: The vertical amplifier is ac coupled to the input. Thus the dc component of the input is blocked and only the ac components of the input signals deflect the beam vertically. This allows observing small ac signals or large dc background.

(iii) Ground: The input to the amplifier is grounded. There will be no vertical deflection. If no voltage is applied to horizontal plates, the spot will be at the position corresponding to the ground. It is useful for measuring voltage with respect to the ground.

14. The chop mode in CRO is used for

1. High frequency Only
2. Low Frequency Only
3. Both high and low frequency Only
4. None of the above

Answer.3. Both high and low frequency Only

Explanation:

Chop: In this mode first input A is displayed for a fraction of a microsecond, then input B for a fraction of microsecond, then input A again, and so on.

In this way, plots of both inputs can be drawn at the same time.

The chop mode is useful with low-frequency signals, while the alternate mode is useful for high-frequency signals.

15. The Z-axis control in CRO is used for

1. Increases the Brightness
2. Decreases the focus
3. Controls sharpness
4. Maintains the focus zero