The structure and working process of the oscilloscope

1. Basic structure
① The Y-axis system
consists of attenuators, expanders and extension lines. Its main function is to expand the voltage of the measured signal to reach the appropriate level to drive the electron beam to deflect vertically.

② The X-axis system
consists of a trigger shaping circuit, a scanning generator and an x-axis expander. Its function is to generate and expand the scanning sawtooth wave, driving the electron beam to scan horizontally. The trigger shaping circuit ensures that the waveform displayed on the fluorescent screen is stable, which is convenient for observing the signal waveform.

③ The Z-axis system
consists of an oscilloscope, a brightness enhancement circuit, a power supply and a calibration signal generator. The oscilloscope consists of an electron gun, an X-axis deflection plate, a Y-axis deflection plate and a fluorescent screen. Its main function is to convert electrical signals into optical signals for displaying the waveform of the measured signal. The function of the brightness enhancement circuit is to brighten the light trace in the forward direction of the signal scan and to blank the light trace in the return direction of the signal scan. The power supply circuit converts the AC mains into a variety of high and low voltage power supplies to meet the needs of the oscilloscope and other circuit operations. The calibration signal generator provides a square wave signal with very accurate height and period for calibrating the relevant functional indicators of the oscilloscope.

2. During the operation,
the measured signal voltage is added to the Y-axis input terminal through the oscilloscope probe. After attenuation, pre-expansion and inversion, it is extended by the extension line and expanded by the Y-axis post-expansion device. A sufficiently large push-pull signal is output and added to the vertical deflection plate of the oscilloscope to control the vertical deviation of the electron beam.

In order to display a stable waveform and make the starting point of each scan correspond to the same phase point of the measured signal, the measured signal can be sent to the trigger shaping circuit. The trigger shaping circuit is triggered at a certain electron and polarity of the measured signal, and outputs a trigger pulse to prompt the scanning generator to generate a sawtooth wave voltage, which is widened by the x-axis expander to become a push-pull signal added to the horizontal deflection plate of the oscilloscope to control the horizontal deflection of the electron beam (i.e. the scanning process). At the same time, the scanning signal generator also outputs a brightening pulse with a pulse width equal to the scanning positive process, and is added to the gate of the oscilloscope through the z-axis system to brighten the flashing light trace.