1, the horizontal working mode of the oscilloscope is XY, and it is not in the self-excited scanning state;

2. Adjust the horizontal working mode to "automatic", and the scanning speed can be adjusted to a suitable position according to the frequency of the square wave (some oscilloscopes automatically leave the XY working mode when scanning);

3, a, moderate brightness, small and round focus. When measuring vertical parameters, let the waveform amplitude account for 60% of the amplitude on the screen, and when measuring horizontal parameters, try to display the whole screen for one or two periods;

4, reading can get four significant figures, mainly determined by the scale of the oscilloscope, each grid is divided into five small grids. For example, the vertical deflection factor is 5V/div, and the number of units occupied by the vertical peak is 6.2a, then the latter one has to be estimated. If it is 6.23 cells, then VPP = 31.15; The same is true in horizontal direction.