The first picture shows the waveform tested at low temperature, and the second picture shows the waveform tested at normal temperature. Why does the STOP signal lag when tested at low temperature? It is because normally the falling edge position of the first echo is collected, but abnormally the rising edge position of the second echo is collected. Some samples also show lag at high temperature, but it is always unstable. Not all samples will be delayed, and the delayed samples will also show a normal waveform and a second waveform at some point. So why does this happen? Is it because the temperature interferes with the stop signal?
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