Oscilloscope is a widely used electronic measuring instrument. It can transform electrical signals invisible to the naked eye into visible images, which is convenient for people to study the changing process of various electrical phenomena. Oscilloscope uses a narrow electron beam composed of high-speed electrons to hit the screen coated with fluorescent substances, which can produce tiny light spots (this is the working principle of traditional analog oscilloscope). Under the action of the measured signal, the electron beam, like a pen tip, can draw the curve of the instantaneous value of the measured signal on the screen. Oscilloscope can be used to observe the waveform curves of different signal amplitudes changing with time, and can also be used to test various electric quantities, such as voltage, current, frequency, phase difference and amplitude modulation.
The display circuit includes oscilloscope tube and its control circuit. Oscilloscope is a special kind of electron tube and an important part of oscilloscope. Oscilloscope consists of three parts: electron gun, deflection system and fluorescent screen.
According to the principle of oscilloscope tube, when a DC voltage is applied to a pair of deflection plates, the light spot will have a fixed displacement on the screen, which is proportional to the applied DC voltage. If two DC voltages are applied to the vertical and horizontal deflection plates at the same time, the position of the light spot on the fluorescent screen is determined by the displacement in both directions.