Key waveform capture
Time:2024-02-07
Views:285
Today I had a sudden impulse and wanted to see what the waveform of pressing and releasing buttons looks like. I used a DS4054A oscilloscope with a bandwidth of 500M from Puyuan, and the circuit was a simple resistor connected in series with the button to ground.
During the process of detecting the waveform, it was found that the minimum holding time for the low level when I immediately release the button is 50ms. Of course, this is just a reference value. Depending on the quality of the switch, personal reaction speed may vary, and the minimum holding time for low levels may also vary. The popular saying online is that the shortest time for a button to close at once is about 120ms. For reference information, please refer to the end of the article.
The minimum low-level holding time I tested is as follows, which is 50ms:
50ms per grid
Normal speed button waveform, low-level hold time 137ms:
Reading reference oscilloscope parameters in the upper left corner
During the testing process, it was found that the waveform jitter when the button was pressed was smaller than the jitter time and degree when the button was released, so only the waveform released by the button twice was captured.
From the figure, it can be seen that the jitter time when the button is released is 1.076ms
The shaking during the release of another button first appeared as a spike, followed by continuous shaking after a gap of about 1.5ms, with a total shaking time of 2.510ms.
From the test results, if you want the button to respond quickly, you can process it with a jitter time of 5-8ms and a minimum low-level holding time of 30ms for the button. The 30ms here includes the jitter time for pressing and releasing, which is considered a reliable low-level processing time of only 14-20ms.
Regarding the explanation of this article: Due to the bandwidth and rise time limitations of the oscilloscope, it may not be possible to better record button waveform jitter. However, for the processing of button jitter, time accuracy is already sufficient.
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