The electron gun assembly consists of an indirectly heated cathode, a control grid, a focussing anode and an accelerating anode and it is used to produce a focused beam of electrons. This prevents the walls from charging to a high negative potential. This coating is electrically connected to the accelerating anode so that the electrons which accidentally strike the walls are returned to the anode. The inner wall of CRT between the neck and screen are usually coated with a conducting material known as aquadag. It is a conical highly evacuated glass housing which maintains vacuum inside it and supports various electrodes. Now we will discuss each part of the CRT in detail.
The figure below shows various parts of a cathode ray tube (CRT). As a result, the electrical signal waveform is displayed visually. The electron beam is deflected during its journey in response to the applied electrical signal. The cathode ray tube or CRT is a vacuum tube of special geometrical shape which converts an electrical signal into a visual one.Ī CRT makes available a large number of electrons which are accelerated to high velocity and are brought to focus on a fluorescent screen where it produces a spot when strikes it. Since CRT is the heart of the oscilloscope, we are going to discuss its various components in detail. The signal to be viewed is supplied to the vertical deflection plate through the vertical amplifier, so that it can amplify the signal to a level that will provide usable deflection of the electron beam.Īs the electron beam is deflected in X-axis as well as Y-axis, a triggering circuit is provided for synchronizing these two types of deflections so that horizontal deflection starts at the same point of the input vertical signal each time it sweeps.
Cathode ray oscilloscope generator#
X-axis with constant time dependent rate, a time base generator is provided in the oscilloscope.
To deflect the electron beam on the screen in horizontal direction i.e. Horizontal and vertical deflection plates are fitted between the electron gun and the screen so that these can deflect the beam according to the input signal. Normal voltage supply is required for other control units of the oscilloscope. Low voltage supply is required for the heater of the electron gun to generate the electron beam and high voltage is required for the cathode ray tube to accelerate the beam. By deflecting the beam over the screen in response to the electrical signal, the electrons can be made to act as an electrical pencil of light which produces a spot of light wherever it strikes.įor accomplishing these tasks various electrical signals and voltages are needed, which are provided by the power supply circuit of the oscilloscope. This screen produces a visible spot where the electron beam strikes it. In an oscilloscope, the CRT generates the electron beam which are accelerated to a high velocity and brought to focus on a fluorescent screen. As we can see from the above figure above, a CRO employs a cathode ray tube ( CRT) ,which acts as the heart of the oscilloscope.
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