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What is Cathode Ray Tube?
What is Cathode Ray Tube?
Cathode Ray Tube is a display screen which produces images in the form of the video signal. It is a type of vacuum tube which displays images when the electron beam through electron guns are strikes on the phosphorescent surface. In other Words, the CRT generates the beams, accelerates it at high velocity and deflect it for creating the images on the phosphorous screen so that the beam becomes visible.
How Cathode Ray Tube works?
How Cathode Ray Tube works?
4.2.1 How important Cathode Ray Tube
4.2.1 How important Cathode Ray Tube
•The most vital component in an oscilloscope is the Cathode Ray Tube (CRT) which is very much similar to picture tube in a television set.
•The CRT makes the applied signal visible by the deflection of thin beam of electrons.
•Oscilloscopes depend on the movement of electron beam striking the fluorescent substance coated screen which then produces visible spot.
•Beams are deflected on both X–axis and Y–axis producing output of time–dependent variation of input voltage.
4.2.1 Construction of Cathode Ray Oscilloscope
4.2.1 Construction of Cathode Ray Oscilloscope
a) Cathode Ray Tube
•The cathode ray tube is the vacuum tube which converts the electrical signal into the visual signal.
•The cathode ray tube mainly consists of the electron gun and the electrostatic deflection plates (vertical and horizontal).
•The electron gun produces a focused beam of the electron which is accelerated to high frequency.
•The vertical deflection plate moves the beams up and down and the horizontal beam moved the electrons beams left to right.
b) Electronic Gun Assembly
•The electron gun emits the electrons and forms them into a beam.
•The electron gun mainly consists of a heater, cathode, a grid, a pre-accelerating anode, a focusing anode and an accelerating anode.
•For gaining the high emission of electrons at the moderate temperature, the layers of barium and strontium is deposited on the end of the cathode.
•After the emission of an electron from the cathode grid, it passes through the control grid.
•The control grid is usually a nickel cylinder with a centrally located co-axial with the CRT axis.
•It controls the intensity of the emitted electron from the cathode.
c) Deflecting Plate
•The electron beam after leaving the electron gun passes through the two pairs of the deflecting plate.
•The pair of plate producing the vertical deflection is called a vertical deflecting plate or Y plates, and the pair of the plate which is used for horizontal deflection is called horizontal deflection plate or X plates.
d) Screen for CRT
•The front of the CRT is called the face plate. It is flat for screen sized up to about 100mm×100mm.
•The screen of the CRT is slightly curved for larger displays.
•The face plate is formed by pressing the molten glass into a mould and then annealing it.
•The inside surface of the faceplate is coated with phosphor crystal.
•The phosphor converts electrical energy into light energy.
•When an electronics beam strike phosphor crystal, it raises their energy level and hence light is emitted during phosphorous crystallisation. This phenomenon is called fluorescence.
e) Glass Envelope
•It is a highly evacuated conical shape structure.
•The inner surface of the CRT between the neck and the screen is coated with the aquadag.
•The aquadag is a conducting material and act as a high-voltage electrode.
•The coating surface is electrically connected to the accelerating anode and hence help the electron to be the focus.
4.2.2 How Cathode Ray Tube Works?
4.2.2 How Cathode Ray Tube Works?
Figure 4.2.2: Cathode Ray Tube Construction
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