Better waveform observation, revealing the four capture methods of oscilloscope

    Usually after Auto Setup, the waveform will appear on the screen, and then we can perform measurement and analysis, but Auto Setup cannot guarantee that the signal is captured with high fidelity. High-fidelity signal capture is the first element, otherwise the subsequent measurement and analysis will be meaningless. So how can we better observe the waveform? You will know after reading this article. How to 
better observe the waveform is essentially to focus on measuring and analyzing the points of interest. How to capture the waveform with high fidelity starts with the process of the oscilloscope processing the signal. After the signal is processed by the front-end circuit of the oscilloscope, it comes to the ADC for analog-to-digital conversion. Next, the signal needs to be reconstructed and restored. This is the focus of this article, the capture mode of the oscilloscope. There are generally four capture modes, and different capture modes are suitable for observing different signals. Next, I will give you a brief introduction to the way the oscilloscope handles sampling points, that is, the capture mode of the oscilloscope. Standard capture mode The first thing to introduce is the standard capture mode. In this mode, the oscilloscope will sample the collected signal at equal intervals. The standard capture working mode also guarantees the original state of the signal to the greatest extent. For most waveforms, this mode can produce the best display effect. The following is the default capture mode of the ZDS2000 series oscilloscope.   Peak capture mode Next is the peak capture mode. Just look at the name to know what it means. It is to collect the maximum and minimum values ​​in a sampling interval signal. In this mode, occasional narrow pulse widths can be effectively observed. It is very practical in capturing high-frequency glitches. It can obtain the envelope of the signal or narrow pulses that may be lost. Using the peak capture mode will make the noise displayed by the waveform more obvious. Average capture mode   The third one is the average capture mode. The name is also very easy to understand. It is to collect N screen signals, align them at the trigger position, and then perform an average operation. Using the average capture mode, while reducing noise, it maintains the original bandwidth. Filtering out noise is conducive to measuring the signal. It is suitable for observing periodic repetitive signals. Its filtering effect improves the vertical resolution of the oscilloscope. It is worth mentioning that average capture is particularly suitable for performing harmonic analysis or power quality analysis.   High-resolution capture mode Finally, there is the high-resolution capture mode. For example, its working principle is to divide a waveform into 5 parts, and then average each point of one waveform, and finally one waveform becomes 5 points. This processing method can effectively improve the equivalent resolution of the system, which is essentially a digital filter. The more sampling points used for averaging, the more the resolution is improved, and the displayed waveform is smoother, thereby achieving the purpose of reducing noise. It should be noted that high resolution is to average the adjacent points of a waveform, so this mode is to sacrifice bandwidth for non-repeating signals to improve the test accuracy, so it is not suitable for testing high-frequency signals, and is suitable for observing high-resolution and low-bandwidth waveforms.   Comparison of the four capture modes After understanding the working principles of the four capture modes, let's make a comparison. When inputting the same signal, noise can be observed in the standard capture mode, the noise of the signal is more obvious in the peak capture mode, and almost no random noise is seen in the average capture mode and high-resolution capture mode. According to the type of the measured signal and the test point that needs to be paid attention to, setting the corresponding capture mode can help us better observe the waveform and find and solve problems faster.