Objective: Study the physical principles of the time-resolved display of electrical signals using an oscilloscope
The student oscilloscope can be used to study the physical principles of the time-resolved display of electrical signals on a fluorescent screen. In a Braun tube, a focused electron beam is generated, and the point at which it falls on the fluorescent screen is observed as a spot of green light. When the electron beam is deflected by a sawtooth voltage applied between a pair of plates, it moves at a constant speed from left to right across the screen, then flies back to the starting point. This process is repeated cyclically at a frequency that can be adjusted. The time-dependent voltage that is to be displayed is applied to a coil outside the tube, so that the beam is deflected vertically in the magnetic field of the coil. The time-dependence of the signal is resolved by the simultaneous horizontal motion of the electron beam and displayed on the fluorescent screen.