【Principle of oscilloscope trigger】
The trigger system and sampling system of the oscilloscope are an important part of the oscilloscope. The sampling system is responsible for digitizing the analog signal, but the signal is constantly coming, which part should be displayed on the interface of the oscilloscope?
If the oscilloscope does not have a trigger system, and the sampled waveforms are superimposed at intervals or at random times, due to the uncertainty and irregularity of the sampling positions, the very chaotic waveform display in Figure 1 will appear, which looks like a waveform scrolling back and forth on the screen.
Figure 1 Waveform sampling without triggering the system
This chaotic phenomenon is consistent with the phenomenon of trigger instability on the oscilloscope. This is shown in Figure 2 below.
This is achieved by the trigger system. The principle of triggering is to monitor the signal flow all the time, if the signal is found to meet the set trigger conditions, the trigger records the signal that meets the conditions and starts sampling; after the data acquisition is completed, the signal is processed and displayed by the controller. This is shown in Figure 2.
Figure 3 Trigger process
A key factor in the trigger condition of an oscilloscope is the trigger level, which in most cases is referenced by a DC level, and the moment when the voltage of the signal exceeds that DC level is used as the starting point for sampling the waveform. Because the starting sample position is regular, the waveform that has been sampled multiple times appears to be stable when superimposed. As shown in Figure 3:
Figure 4 Waveform sampling with stable triggering
The trigger function of the oscilloscope can make the waveform stable on the one hand, and the waveform can no longer shake left and right; on the other hand, it can shorten the time of user debugging, and only the signal that meets the trigger conditions will be captured and displayed.
Dynamically adjusting the trigger level of the oscilloscope allows you to observe the dynamic change of the position of the stable trigger of the waveform, as shown in Dynamic Figure 5 below. #示波器 #
