Question

What is the working principle of a CRO?

Answer 1

A CRO (Cathode Ray Oscilloscope) is an electronic device used to display and analyze the waveform of electronic signals. It works by converting electrical signals into visible waveforms on a screen, allowing engineers and scientists to visualize and measure various aspects of the signal like amplitude, frequency, and timing.

Here's the basic working principle of a CRO:

1. Electron Beam Generation:
   

   Inside the CRO, there is a cathode (negative electrode) that heats up and releases electrons. These electrons are accelerated by high voltage and form a beam.

1. Beam Control:
   

   The electron beam is directed and focused into a narrow, controlled beam by a system of magnetic or electrostatic fields. The beam is made to move in both horizontal and vertical directions on the screen.

1. Deflection of the Electron Beam:
   

   - Vertical Deflection: The vertical movement of the electron beam is controlled by the input signal. When an electrical signal is fed into the CRO, it influences the vertical deflection plates (or coils in some CROs) that move the beam up or down according to the voltage of the signal.
   - Horizontal Deflection: The horizontal movement is controlled by a time base circuit, which makes the electron beam sweep across the screen from left to right at a constant speed. This sweep represents time.

1. Screen Display:
   

   The electron beam strikes a phosphorescent screen, causing it to glow and leave a trace or spot wherever it hits. As the beam moves across the screen (due to the time base), the trace forms a continuous waveform that represents the input signal.

1. Signal Visualization:
   

   - The vertical axis (Y-axis) represents the amplitude of the signal (the height of the waveform).
   - The horizontal axis (X-axis) represents time (how the signal changes over time).

1. Triggering:
   

   To make the waveform stable and easier to analyze, a triggering system is used. It ensures that the electron beam starts at a specific point on the waveform, so it remains consistent when displayed, preventing the trace from drifting.

In summary, a CRO works by using an electron beam to display electrical signals as waveforms on a phosphorescent screen. By controlling the beam's movement with the input signal and time base, you can observe and measure the characteristics of the signal, such as its shape, frequency, and amplitude.