cathode ray oscilloscope and its applications

cro

1. Cathode Ray Oscilloscope
Satish Chandra

2. Cathode Ray Oscilloscope
•The cathode ray oscilloscope (CRO) is the instrument
which generates the waveform of any electrical quantity.
•The waveform is generated in such a way that the
amplitude of the signal is represented along Y-axis and
the variation in the time is represented along X-axis.
•CRO is the measuring device as well as it can generate
waveforms in terms of amplitude and time because it is
very easy to measure the amplitude of the voltage signal
to determine its intensity.
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

3. Block Diagram of Oscilloscope
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

4. Parts of Oscilloscope
•Cathode Ray Tube
•Time Base Generator
•Vertical Deflection System
•Horizontal Deflection System
•Delay line Circuit
•Trigger Circuit

1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

5. Cathode Ray Tube
•The cathode ray tube consists of an electron gun, vertical
deflection plates, horizontal deflection plates, phosphor
screen and electrode.
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

6. Cathode Ray Tube
•The electron gun generates the beam of an electron when the
voltage is applied to it.
•It must be noted that the voltage applied to the electron gun
is quite low while the voltage applied for accelerating the
beam of electron is very high.
•The beam of an electron when generated by the electron gun
is passed from vertical deflection plate and horizontal
deflection plate and it creates the pattern on the phosphor
screen.
•When the light ray strikes the phosphor screen, a bright spot
or luminous spot is created.

1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

7. Cathode Ray Tube
•The electron beam suffers from deflection due to the
presence of vertical deflection plate and horizontal
deflection plate.
•The extent of deflection is directly dependant on the
signal which is received from the output terminal of the
vertical amplifier and the horizontal amplifier.
•It is due to this deflection phenomenon the luminous
spots are created on different parts of the screen, and
thus waveform can be seen by these luminous spots.
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

8. Time-Base Generator
•The circuit that produces a linearly varying voltage or
current with time is known as Time-Base Generator.
•It is basically a function generator that generates a saw-tooth
waveform of high frequency.
•These circuits are also known as sweep circuits. This is so
because they are used to sweep the beam of electron across
the screen in a horizontal direction in CRO.
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

9. Time Base
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

10. Cathode Ray Tube
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

11. Vertical Amplifier
•The vertical amplifier receives the input from the signal which
is to be measured.
•The vertical amplifier receives the input signal and then
amplifies it so that the signal of high intensity is supplied to
the vertical deflection plate.
•If a low-intensity signal strikes the vertical deflection plate,
the electron beam will not be deflected effectively to create
the bright spots on desired points on the screen.
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

12. Horizontal Amplifier
•The horizontal amplifier generates the signal which provides
voltage to horizontal deflection plates.
•The horizontal deflection plates deflect the beam along the
horizontal direction. This is helpful to create the waveform
along with the time domain.
•The deflection of the electron beam in the horizontal
direction will be effective only when the signal applied from
the output of the horizontal amplifier is high enough to create
the bright spots at the desired location on the phosphor
screen.
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

13. Delay Line Circuit
•When the signal from the vertical amplifier is fed to
the vertical deflection plates, then some part of the
amplified signal is supplied to the time base
generator.
•This trigger pulse generated from the time-based
generator is amplified with the help of the horizontal
amplifier.
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

14. Delay Line Circuit
•After this, it is fed to horizontal deflection plates. This
process requires approximately 100ns.
•Thus, it is crucial to delay the signal generated by the
vertical amplifier too in order to maintain
synchronization.
•The delay line is essential because there is the delay
when any electronic signal passes through the
electronic circuitry.
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

15. Trigger Circuit
•The trigger pulse is generated by the time base
generator to provide synchronization of the signals
obtained from the horizontal and vertical amplifier.
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

16. Working of Cathode Ray Oscilloscope
•The electron gun generates the beam of electrons; these
beam consists of several electrons moving towards phosphor
screen. The control grids are also used in CRT to control the
intensity of electrons.
•The accelerating anodes are used to increase the velocity of
electrons so that they strike the phosphor screen with high
speed and thus forms a bright spot.
•The beam creates the luminous spot at the different points on
the screen. This becomes easy with the help of deflection
plates which deflects the electron beam through various
angles. 1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

17. CRT
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

18. Applications of Oscilloscope
•An oscilloscope is used for voltage measurement,
current measurement, measurement of other
physical quantities after conversion to electrical
form.
•Cathode ray oscilloscope is also used in the
laboratory to study the output waveforms of various
signals. Besides, it can also be used to measure their
phase and frequency.
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur

19. END
CRT
1/11/2020 Dr. Satish Chandra, PPN College, Kanpur