If you can’t use trigger well, you can’t be considered as using an oscilloscope

On the oscilloscope panel, the most prominent function key, apart from the knob, should be the trigger button. For oscilloscope users, the trigger is also the most frequently used button. There is a saying that if you can't play the trigger well, you can't be considered to use the oscilloscope, which shows the importance of the trigger function in the use of the oscilloscope. In

　　some high-speed signals now, the frequency of use of the trigger function has been reduced a lot, and the waveform capture relies more on the indicators of the oscilloscope's own hardware. However, these do not affect the fact that triggering is one of the most important features of the oscilloscope. Because the oscilloscope has a powerful trigger function, it can be used for abnormal signal capture and circuit fault debugging. The trigger of the oscilloscope has two important functions: capturing the signal waveform of interest and determining the time reference zero point, and stably displaying the waveform. In most cases, the waveform can be analyzed stably and reliably only after triggering.

　　Triggering is one of the biggest features that distinguishes digital oscilloscopes from analog oscilloscopes. The trigger function of the digital oscilloscope is very rich. Through the trigger setting, users can see the signal before the trigger and the signal after the trigger. The so-called trigger, according to the professional explanation, is: set certain trigger conditions according to the needs. When a waveform in the waveform stream meets this condition, the oscilloscope captures the waveform and its adjacent parts in real time and displays them on the screen. The uniqueness of the trigger condition is the primary condition for accurate capture. In order to observe more events that occurred before a specific waveform, move the trigger point to the right of the display window for a period of time, which is a delayed trigger; in order to understand more events that occurred after a specific waveform, move the trigger point to the left of the display window for a period of time, which is an advanced trigger.

　　The "triggering" of the oscilloscope is to synchronize the scanning of the oscilloscope with the observed signal, so as to display a stable waveform. Different "trigger modes" are required to meet different observation needs. Now, as the complexity of waveforms observed by oscilloscopes continues to increase, there are more and more trigger modes, such as Hold Off, Edge Trigger, Edge Then Edge Trigger, Edge Transition Trigger, Glitch Trigger, Pattern/State Trigger, Pulse Width Trigger, Runt Trigger, Setup and Hold Trigger, Timeout Trigger, Serial Trigger, etc. However, there are three

　　basic trigger modes of oscilloscopes:

　　the first is "AUTO Mode". In this mode, when no trigger occurs, the scanning system of the oscilloscope will automatically scan according to the set scanning rate; and when a trigger occurs, the scanning system will try to scan according to the frequency of the signal. Therefore, in this mode, regardless of whether the trigger conditions are met, the oscilloscope will generate a scan, and the changing scan lines can be seen on the screen. This is the characteristic of this mode.

　　The second is "normal mode/conventional mode (NORM)", which is different from the automatic mode. In this mode, the oscilloscope will scan only when the trigger condition is met, and will not scan if there is no trigger. Therefore, if there is no trigger in this mode, the analog oscilloscope will not see the scan line, and there will be nothing on the screen. For the digital oscilloscope, the waveform update will not be seen. If you don't understand this, you will often think that the signal is not connected or there is some other fault.

　　The third is "single mode (SINGLE)", which is somewhat similar to the "normal mode", that is, the scan will only be generated when the trigger condition is met, otherwise it will not be scanned. The difference is that once this scan is generated and completed, the scanning system of the oscilloscope will enter a dormant state, and even if there is a signal that meets the trigger condition later, it will no longer scan, that is, it will only scan once for one trigger, that is, single, and the scanning system must be restarted manually to generate the next trigger. Obviously, for ordinary analog oscilloscopes, you often find that you can't see anything in this mode, because the waveform flashes by and the oscilloscope cannot retain it. In most cases, this mode is useless. The above three trigger modes are provided by most oscilloscopes.

　　In actual use, the selection of different trigger modes should be based on the characteristics of the observed signal and the content to be observed. There is no fixed rule, but it is often an interactive process, that is, to understand the characteristics of the signal by selecting different trigger modes, and to select an effective trigger mode based on the characteristics of the signal and the content to be observed. The most important thing in this process is to understand the working mechanism of different trigger modes, understand the characteristics of the observed signal, and clarify the content to be observed.