Kishore Kandhasamy's Interesting Speech

OSCILLOSCOPE in simple version

     CRO is the most powerful device in electronics to measure the DC voltages & AC voltages or sound in the wave forms very easily.

1. Cathode Ray Oscilloscope (CRO):

•       The cathode ray Oscilloscope consists of the following main units.

i. Cathode Ray Tube (CRT)

ii. Power supply Unit

iii. Vertical amplifier

iv. Delay Line

v. Time base or Sweep generator

vi. Horizontal amplifier

vii. Trigger circuit.

• The block diagram of Oscilloscope is shown in figure.

•     CRO is generally referred to as Oscilloscope or simple Scope.
•  The CRO provides a two dimensional visual display of the signal wave shape on a screen.
•  An Oscilloscope can display and also measure many electrical quantities like AC/DC voltage, time, phase relationships, frequency a wide range of waveform characteristics, pressure, strain, temperature and acceleration.

1. Cathode Ray Tube (CRT):

•  It is the heart of the CRO.
•  It produces a sharply focussed beam of electrons accelerated to a very high velocity.
•  This focussed and accelerated beam of electron travels front of the CRT, where it strikes the fluorescent material deposited on the inside face of the CRT with sufficient energy.
• While travelling from the electron gun, the beam passes through a pair of vertical defecting plates and a pair of horizontal deflecting plates.
•  Voltages applied to the horizontal deflecting plates can move the beam in horizontal plane from left to right of the screen.
•  The CRT mainly consists of the following main parts,

          (a). Electron Gun

          (b). Vertical deflecting plates

          (c). Horizontal deflecting plates

          (d). Fluorescent screen

i. Power Supply Unit

•  The power supply consists of high voltage tapping to operate CRT and a low voltage section for other circuits.
•  High voltage is required for accelerating and focussing electrons of CRT while low voltage are required to operate different circuits such as horizontal and vertical amplifiers, time base circuit.

ii. Vertical amplifier:

• The signal waveform to be observed on the screen of CRO is applied to the vertical amplifier.
• The output of this amplifier is fed the vertical deflection plates of the CRT.

• iii. Delay Line:
• The purpose of the delay line is to slow down the arrival of the input waveform at the vertical deflecting plates until the trigger and time base circuits have a chance to start the sweep of the beam.

iv. Time base or Sweep generator:

• It develops a sawtooth waveforms that is used as horizontal deflecting voltage of the CRT.
• The sawtooth voltage is fed to the horizontal amplifier.

v. Horizontal Amplifier:

• The saw tooth voltage from the time base generator is fed to the horizontal amplifier.
• This amplifier includes a phase inverter and produces two simultaneous output waveform.
• A positive going saw tooth is applied to the right hand horizontal deflecting plate

vi. Trigger Circuit:

•  A sample of input waveform is fed to the trigger circuit which produces a trigger pulse.
• This trigger pulse is used to start the time base generator which in turn starts the horizontal sweep of the CRT.
• There are other provisions on front panel of CRO such as intensity control, focus control, horizontal control and vertical position control.