Tutorial On CRO (Cathode Ray Oscilloscope) Working and Applications

The CRO stands for a cathode ray oscilloscope. It is typically divided into four sections which are display, vertical controllers, horizontal controllers, and Triggers. Most of the oscilloscopes are used the probes and they are used for the input of any instrument. We can analyze the waveform by plotting amplitude along with the x-axis and y-axis. The applications of CRO’s mainly involve in the radio, TV receivers, also in laboratory work involving research and design. In modern electronics, the CRO plays an important role in the electronic circuits.

What is a CRO?

The cathode ray oscilloscope is an electronic test instrument, it is used to obtain waveforms when the different input signals are given. In the early days, it is called as an Oscillograph. The oscilloscope observes the changes in the electrical signals over time, thus the voltage and time describe a shape and it is continuously graphed beside a scale. By seeing the waveform, we can analyze some properties like amplitude, frequency, rise time, distortion, time interval and etc.

Cathode Ray Oscilloscope
Cathode Ray Oscilloscope

Block Diagram of CRO

The following block diagram shows the general purpose CRO contraction. The CRO recruit the cathode ray tube and acts as a heat of the oscilloscope. In an oscilloscope, the CRT produces the electron beam which is accelerated to a high velocity and brings to the focal point on a fluorescent screen. Thus, the screen produces a visible spot where the electron beam strikes with it. By detecting the beam above the screen in reply to the electrical signal, the electrons can act as an electrical pencil of light which produces a light where it strikes.

Block Diagram of CRO
Block Diagram of CRO

To complete this task we need various electrical signals and voltages. This provides the power supply circuit of the oscilloscope. Here we will use high voltage and low voltage. The low voltage is used for the heater of the electron gun to generate the electron beam. The high voltage is required for the cathode ray tube to speed up the beam. The normal voltage supply is necessary for other control units of the oscilloscope.

The horizontal and vertical plates are placed between the electron gun and the screen, thus it can detect the beam according to the input signal. Just before detecting the electron beam on the screen in the horizontal direction which is in X-axis a constant time-dependent rate, a time base generator is given by the oscillator. The signals are passed from the vertical deflection plate through the vertical amplifier. Thus, it can amplify the signal to a level will be provided the deflection of the electron beam.

If the electron beam is detected in the X-axis and the Y- axis a trigger circuit is given for the synchronizing these two types detections. Hence the horizontal deflection starts at the same point of the input signal.


Working of CRO

The following circuit diagram shows the basic circuit of a cathode ray oscilloscope. In this, we will discuss important parts of the oscilloscope.

Working of CRO
Working of CRO

Vertical Deflection System

The main function of this amplifier is to amplify the weak signal so that the amplified signal can produce the desired signal. To examine the input signals are penetrated to the vertical deflection plates through the input attenuator and number of amplifier stages.

Horizontal Deflection System

The vertical and horizontal system consists of horizontal amplifiers to amplify the weak input signals, but it is different to the vertical deflection system. The horizontal deflection plates are penetrated by a sweep voltage that gives a time base. By seeing the circuit diagram the sawtooth sweep generator is triggered by the synchronizing amplifier while the sweep selector switches in the internal position. So the trigger saw tooth generator gives the input to the horizontal amplifier by following the mechanism.Here we will discuss the four types of sweeps.

Recurrent Sweep

As the name, itself says that the saw tooth is respective that is a new sweep is started immodestly at the end of the previous sweep.

Triggered Sweep

Sometimes the waveform should be observed that it may not be predicted, thus the desired that the sweep circuit remains inoperative and the sweep should be initiated by the waveform under the examination. In these cases, we will use the triggered sweep.

Driven Sweep

In general, the drive sweep is used when the sweep is a free running but it is a triggered by the signal under the test.

Non-Saw Tooth Sweep

This sweep is used to find the difference between the two voltages. By using the non-sawtooth sweep we can compare the frequency of the input voltages.


The synchronization is done to produce the stationary pattern. The synchronization is between the sweep and the signal should measure. There are some sources of synchronization which can be selected by the synchronization selector. Which are discussed below.


In this the signal is measured by the vertical amplifier and the trigger is abstained by the signal.


In the external trigger, the external trigger should be present.


The line trigger is produced by the power supply.

Intensity Modulation

This modulation is produced by inserting the signal between the ground and cathode. This modulation causes by brightening the display.

Positioning Control

By applying the small independent internal direct voltage source to the detecting plates through the potentiometer the position can be controlled and also we can control the position of the signal.

Intensity Control

The intensity has a difference by changing the grid potential with respect to the cathode.

Applications of CRO

  • Voltage measurement
  • Current measurement
  • Examination of waveform
  • Measurement of phase and frequency

Uses of CRO

In laboratory, the CRO can be used as

  • It can display different types of waveforms
  • It can measure short time interval
  • In voltmeter, it can measure potential difference

In this article, we have discussed the working of CRO and its application. By reading this article you have known some basic knowledge about the working & applications of the CRO. If you have any queries regarding this article or to implement the ECE & EEE projects, please comment in the below section. Here is the question for you, what are the functions of the CRO?

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    This article is very informative and useful. It is written in simple language and easy to understand.

  2. Sudarshan says:


    This explanation is easy and useful information..all
    Simply super.

  3. Tarun Agarwal says:

    Hi Ajay
    You’re welcome

  4. Raghunandan says:

    Sir please give me some new ideas of projects related to ece branch

  5. Vivek bhagat says:

    Thank you it its very easy to understand for me.
    Easy language is used.
    Now I can teach anybody.
    Once again thank you.
    God bless you.

  6. Srilakshmiitham says:

    Super I loved it

    1. Tarun Agarwal says:

      Hi Srilakshmi
      Thank you so much

    1. Tarun Agarwal says:

      Hi Srilakshmi
      Thank you so much

  7. Prasang Singhal says:

    I loved the content very much. It helps me a lot ..

  8. Vanilla ruth mutinda says:

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    God blesss you abandantly

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