How to choose the oscilloscope sampling rate

　　The sampling rate of the oscilloscope depends on the object to be measured. Under the premise of satisfying the bandwidth, it is hoped that the minimum sampling interval (the inverse of the sampling rate) can capture the signal details you need. There are some empirical formulas for sampling rates in the industry, but they are basically derived for the bandwidth of the oscilloscope. In practical applications, it is best not to use an oscilloscope to measure signals of the same frequency. If the bandwidth of the oscilloscope selected for a sine wave is more than 3 times the frequency of the sine signal to be measured, the sampling rate is 4 to 5 times the bandwidth, which is actually 12 to 15 times the signal; if it is other waveforms, ensure that the sampling rate is sufficient to capture the signal details.

　　If you are using an oscilloscope, you can verify whether the sampling rate is sufficient by the following method: stop the waveform, zoom in on the waveform, and if you find that the waveform has changed (such as certain amplitudes), it means that the sampling rate is not enough, otherwise it is fine. In addition, you can also use the dot display to analyze whether the sampling rate is sufficient.

　　Question 2: How to understand the sentence "When checking whether the sampling rate of a waveform is sufficient, stop the waveform and amplify the waveform. If changes are found in the waveform (such as certain amplitudes), it means that the sampling rate is not enough. Otherwise, there is no problem. You can also use the point display to analyze whether the sampling rate is sufficient."?

　　A: The object under test was a signal that looked random and changed rapidly, and the user set the trigger level to about -13V. After the waveform was acquired, I wanted to zoom in on the measurement details, but I found that when I changed the oscilloscope time base (SEC/DIV) setting, the signal amplitude suddenly became smaller. I changed the oscilloscope to dot display and found that it seemed that the number of points (storage depth) was not enough. However, after comparing the dot display and the vector display, I found that if the vector display has a certain degree of credibility, then there is a sudden change in the signal in the current two sampling intervals (the inverse of the sampling rate), but it has not been acquired (the sampling interval is not fine enough, that is, the sampling rate is not high enough). I changed to an oscilloscope with the same storage depth but a higher sampling rate, and found that the problem disappeared.

　　Memory depth also affects the actual maximum sampling rate that can be used with an oscilloscope. Too shallow a memory depth can be a problem because the memory depth may limit the maximum sampling rate that can be used, but in reality, the sampling rate is not enough and signal details are lost. Not deep enough memory depth may result in a low actual sampling rate, which has little to do with the manufacturer's specifications.