A cathode ray oscilloscope8/12/2023 ![]() ![]() Thus, the voltage applied simultaneously to X and Y plates, give control of the beam and the spot of light moves in both, i.e., X and Y directions. The second pair of plates is kept horizontal but produces deflection in the vertical direction and, is therefore, called the vertical deflection plates or Y-plates. Accordingly, these plates, mounted in the vertical plane, are called horizontal deflection plates or X-plates. On leaving the electrostatic field of the plates, the electron beam travels along a straight line at an angle with the axis and hits the screen. If deflection in the horizontal direction is desired, voltage is applied to the plates kept vertical and the beam is attracted towards the positive plate. One pair of these parallel plates is kept vertical while the other pair is kept horizontal. 1, two pairs of deflecting plates are shown, which provide electrostatic deflection and are kept next to the focusing system. The electron beam in a cathode-ray tube can be deflected from its normal position along the axis of the tube by either electrostatic or magnetic means. The second anode also has an aperture to permit a well-defined beam to pass through it. Both these anodes are kept highly positive with respect to the cathode but the potential of the first one is usually lower than that of the second anode. The first and second anode of the electron gun provides an electron lens system which focusses the beam into a fine spot on the screen. To bring it to a sharp focus at the screen electrostatic focussing is employed. The electron beam from accelerating electrode tends to diverge due to mutual repulsion between electrons. The first and second anode together provide necessary focusing to the electron beam so that it produces a high intensity light spot on the screen. ![]() The second anode which is given a very high positive potential of the order of 2000 volt or more, accelerates the electron beam. The positive voltage applied on this first anode focusses the beam of electrons. Hence a focusing electrode (second anode) is placed next to the accelerating electrode. As this narrow electron beam travels further from the accelerating electrode, it tends to spread because of mutual repulsion between electrons. ![]() It is given a high positive potential and the apertures eliminate electrons which diverge from the beam. ![]() Next to control grid is the accelerating electrode (first anode) having one or more apertures. It is given a negative potential with respect to cathode. The control grid which surrounds it has a small aperture in the centre of end surface. The electrons are produced by an indirectly heated cathode of cylindrical shape. The construction of an electron gun is shown in Fig. Second or final anode to provide further acceleration and focussing.Focussing electrode of first anode for focussing the electron beam into a fine spot.Accelerating electrode for attracting the electrons.Control grid for varying the electron current density.Thermionic cathode for emission of electrons.The function of the electron gun is to produce, accelerate and focus the election beam to give a fine spot on the fluorescent screen. The essential parts of a typical cathode ray tube are shown in Fig. Fluorescent screen, upon which the electron beam is focussed to create a well-defined spot.Deflecting plate, which is an arrangement for deflecting the beam either horizontally or vertically.Electron gun, which is an arrangement for producing and focusing an electron beam.It converts a varying voltage into a visible waveform. 1: A general sketch of Cathode ray Oscilloscope Cathode Ray Tube: When this electron beam impinges upon a fluorescent screen, a bright luminous spot is produced there which shows and follows faithfully the variation of potential difference without any time lag.Ī cathode ray oscilloscope consists of the following main constituents:įig. When a varying potential difference is established across two plates between which the beam is passing, it is deflected and moves in accordance with the variation of potential difference. Since the inertia of cathode rays (electron beam) is very small, they can follow the alterations of very high frequency fields and thus electron beam serves as a practically inertia-less pointer. In this device, the cathode rays are deflected by an electric and magnetic field and of producing scintillations on a fluorescent screen. Cathode Ray Oscilloscope (CRO) is an electronic equipment which gives a visual representation of electrical quantities such as voltage and current waveforms in an electrical circuit. ![]()
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