The waveform measured on the oscilloscope is constantly shaking up and down or left and right. Perhaps the measurement drift of the oscilloscope itself is too serious. You can change a good oscilloscope and test whether it keeps shaking up and down. If not, it proves to be the problem of the measuring instrument itself. If it is possible, it is a connection problem.

It is also possible that the trigger is unstable. Triggering has two main functions:

1, isolate the signal of interest;

2. Synchronous waveform (stable display waveform). When the trigger is unstable, it will cause the measured waveform to shake up and down continuously. In order to understand the trigger more vividly, we can use a very sour sentence to describe it: the so-called trigger means "staying at this moment" and can be understood as "waiting for that moment".

Extended data:

According to the different classification of structure and performance:

① Ordinary oscilloscope. The circuit structure is simple, the frequency band is narrow and the scanning linearity is poor. It is only used to observe the waveform.

② Multifunctional oscilloscope. Wide frequency band, good scanning linearity, and can quantitatively test DC, low frequency, high frequency, ultra-high frequency signals and pulse signals. With the help of amplitude calibrator and time calibrator, the measurement accuracy can reach 5%.

③ Multi-line oscilloscope. Using multiple oscilloscopes, the waveforms of more than two signals with the same frequency can be displayed on the screen at the same time, with no time difference and accurate time sequence relationship.

④ Multi-channel oscilloscope. Using the structure of electronic switch and gate circuit, the waveforms of more than two signals with the same frequency can be displayed on the screen of a single beam oscilloscope tube at the same time. However, there is a time difference and the time sequence relationship is inaccurate.

Baidu encyclopedia-oscilloscope