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Errors arising from measurements with mechanical stopwatches

Errors resulting from measurements made with mechanical stopwatches can be categorized in two ways：

(1) For short time measurements (within a few tens of seconds), the errors are mainly by meter and reading errors；

(2) For long measurements (more than 1min), the error is mainly the difference between the stopwatch movement and the standard time. This error varies for different stopwatches. Therefore, before long time measurement, the stopwatch should be calibrated with a standard clock.