The accelerating anodes are at a high positive potential and hence they converge the beam at a point on the screen.Īfter moving from the accelerating anode, the beam comes under the effect of the deflecting plates. Hence the intensity of light depends on the negative potential of the control grid.Īfter moving the control grid the electron beam passing through the focusing and accelerating anodes. If the negative potential on the control grid is low, then the bright spot is produced. Thus, the dim spot is produced on the lightning screen. If the control grid has high negative potential, then it allows only a few electrons to pass through it. The control grid controls the intensity of electron in the vacuum tube. When the electron is injected through the electron gun, it passes through the control grid. The coating surface is electrically connected to the accelerating anode and hence help the electron to be the focus. The aquadag is a conducting material and act as a high-voltage electrode. The inner surface of the CRT between the neck and the screen is coated with the aquadag. It is a highly evacuated conical shape structure. When an electronics beam strike phosphor crystal, it raises their energy level and hence light is emitted during phosphorous crystallisation. The phosphor converts electrical energy into light energy. The inside surface of the faceplate is coated with phosphor crystal. The face plate is formed by pressing the molten glass into a mould and then annealing it. The screen of the CRT is slightly curved for larger displays. It is flat for screen sized up to about 100mm×100mm. The front of the CRT is called the face 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. The electron beam after leaving the electron gun passes through the two pairs of the deflecting plate. The CRO uses an electrostatic focusing tube. There are two methods of focusing on the electron beam. The pre-accelerating and accelerating anode are connected to 1500v, and the focusing electrode is connected to 500 v. The electron beam is focused on focusing electrodes and then passes through the vertical and horizontal deflection plates and then goes on to the fluorescent lamp. The electron while passing through the control grid is accelerated by a high positive potential which is applied to the pre-accelerating or accelerating nodes. It controls the intensity of the emitted electron from the cathode. The control grid is usually a nickel cylinder with a centrally located co-axial with the CRT axis. 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.Īfter the emission of an electron from the cathode grid, it passes through the control grid. The electron gun mainly consists a heater, cathode, a grid, a pre-accelerating anode, a focusing anode and an accelerating anode. The electron gun emits the electrons and forms them into a beam. These movements are independent to each other and hence the beam may be positioned anywhere on the screen. The vertical deflection plate moves the beams up and down and the horizontal beam moved the electrons beams left to right. The cathode ray tube mainly consists 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 cathode ray tube is the vacuum tube which converts the electrical signal into the visual signal. Their parts are explained below in details. The main parts of the cathode ray oscilloscope are as follows. Thus, CRO provides a means of the visualising time-varying voltage. When the input voltage moves very fast on the screen, the display on the screen appears stationary. The vertical voltage moves the luminous spot up and down on the screen. The vertical voltage is the voltage under investigation. The horizontal voltage moves the luminous spot periodically in a horizontal direction from left to right over the display area or screen. The normal form of the CRO uses a horizontal input voltage which is an internally generated ramp voltage called “time base”. This luminous spot is produced by a beam of electrons striking on a fluorescent screen. The CRO has Stylus (i.e., a luminous spot) which move over the display area in response to an input voltage. It is also used for knowing the waveforms, transient phenomenon, and other time-varying quantity from a very low-frequency range to the radio frequencies. Thus, the other physical quantity like current, strain, acceleration, pressure, are converted into the voltage with the help of the transducer and thus represent on a CRO.
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