How to choose and use the oscilloscope's trigger mode in practice?
In actual use, the selection of different trigger modes must be judged based on the characteristics of the signal being observed and the content to be observed. There are no fixed rules, but it is often an interactive process, that is, understanding the characteristics of the signal by selecting different trigger modes , and select an effective trigger mode based on the characteristics of the signal and what you want to observe. The most important thing in this process is to understand the working mechanisms of different trigger modes, understand the characteristics of the observed signal, and clarify what is to be observed.
Generally speaking, when you don't know much about the characteristics of the signal, you should choose the automatic mode, because at this time the oscilloscope will scan no matter what the signal is, and you can at least see something on the screen, even if it is just a scan line. Well, not nothing. Once there are scan lines, you can "find" the waveform by adjusting parameters such as vertical gain, vertical position, and time base rate, and then stabilize the waveform by selecting the trigger source, trigger edge, trigger level, etc. For analog oscilloscopes, as long as the signal is periodic, its frequency is within a range suitable for observation by the corresponding oscilloscope, and it is not too complex, a general understanding of the signal can generally be achieved through such steps, and further observations can be made as needed. .
For the normal mode, many friends may feel that there is no difference in the observation effect from the automatic mode. It is often the case that when the trigger mode is switched between automatic and normal, the screen waveform does not change. However, this situation is often only Occurs when the observed signal is some relatively simple periodic signal. The function of the normal mode is to observe the details of the waveform, especially for more complex signals, such as video synchronization signals. Why do you say this way? This is because in order to observe details, we must increase the time base scan rate to expand the waveform. When we do this, the frequency of the observed signal becomes lower relative to the oscilloscope scan rate, which means that the oscilloscope may scan many times between triggers. In this case, if we select the automatic mode at this time, the oscilloscope will actually perform all these sweeps, and the result is that the waveforms corresponding to these sweeps (which are not generated by the trigger) will be together with the waveforms corresponding to the trigger sweeps. display, resulting in aliasing of displayed waveforms, so the waveform we want to see cannot be clearly displayed. And if we choose the normal mode, the oscilloscope will not actually perform these scans between triggers. It will only perform the scans generated by the trigger, thus only displaying the waveforms associated with the trigger that we want to see, so that The waveform will be clearer, which is the function of normal trigger mode.
As for the single-shot mode, as mentioned above, it is basically difficult to use for ordinary analog oscilloscopes, but it is a very useful trigger mode for digital storage oscilloscopes. In a digital storage oscilloscope, use single trigger mode to capture a single occurrence or multiple occurrences of a signal that is not too periodic. Although the normal mode can also capture a single signal, if the signal is multiple times instead of a single time, the scan triggered by the subsequent signal in the normal mode will erase the previously captured results, so it will not be possible. to a stable waveform. At this time, there is no such problem if the single-shot mode is used. That is to say, the single-shot mode trigger has the ability to select one signal from multiple occurrences.
