The intensity of the electron beam depends upon the number of electrons emitted from the cathode. And an aperture of about 0.25 mm is drilled in the cap of the grid for the electrons to flow through. This is usually a metal cup of low permeability Steel about 15 mm in diameter 15 mm long. This control grid is usually a Nickel cylinder with a centrally located hole coaxial with the CRT axis. These electrons past through a small hole in the control grid. The typical values of current and voltage required by an indirectly heated cathode are 600 mA at 6. A layer of barium and Strontium oxide is deposited on the end of the cathode which is a cylinder to obtain high emission of electrons at moderate temperatures. Large and medium-sized high-performance tubes operate at very high voltages and these leads are usually bought out through the sides of the glass envelope.Įlectrons are emitted from the indirectly heated cathode. In smaller CRT’s connections to the various electrodes are brought out through pins in the base or the tube as shown in the figure. The source of focused and accelerated beam is the electron gun, which emits electrons and forms them into a beam consists of a heater, cathode, a grid, a pre-accelerating anode, a focusing anode and accelerating anode. The working parts of a CRT are enclosed in an evacuated glass envelope so that the emitted electrons are able to move about freely from one end of the tube to other. This two movements i.e horizontal and vertical are independent of each other and thus the beam may be positioned anywhere on the screen. Voltage applied to one pair plates move the beam vertically up and down and the voltages applied to other pair of plates move the beam horizontally from one side to another. Voltages applied to these plates deflects the beam. After leaving the electron gun the electron beam passes through two pairs of electrostatic deflection plates. This focused beam of electrons strikes the fluorescent screen with sufficient energy to cause a luminous spot on the screen. It produces a sharply focused beam of electrons which are accelerated to high velocity. In cathode ray oscilloscope , this is the part from where electrons are born initially. The below figure shows construction of Cathode Ray Oscilloscope. This textbook “ Electrical and Electronics Measurements by S. Construction of Cathode Ray Oscilloscope :Ī cathode ray oscilloscope consists of a cathode ray tube which is the heart of the tube and some additional circuitry to operate the CRT.The main parts of a CRT Most present day oscilloscopes are capable of accepting two or more inputs displaying them simultaneously. Although, most oscilloscope are monochromatic, colour oscilloscope are finding increasing applications in computers and in television. They are now available which can measure frequencies upto 1GHz and observer events as small as 20Hz in duration. However, it is possible to convert current, strain, acceleration, pressure and other physical quantities into voltages with the help of transducers and thus to present visual representations of a wide variety of dynamic phenomena on CRO’s.In this, I will explain Cathode Ray Oscilloscope Working Principle & Construction.Ĭathode Ray Oscilloscopes are used to investigate waveforms, transient phenomena and other time varying quantities from a very low frequency range to the radio frequencies. Cathode Ray Oscilloscopes operate on voltages. Cathode Ray Oscilloscope is a very useful and versatile laboratory instrument used for display, measurement and analysis of waveforms and other phenomena in electrical and electronic circuits.CRO’s are in fact very fast X-Y plotters, displaying an input signal versus another signal versus time.
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