Stopwatch is a common time measuring instrument. It can also be called mechanical stop watch. It is composed of pause button, spring handle and minute needle. It uses the isochronism of the pendulum to control the pointer rotation and timing. On its front is a large dial with a small dial above it. The second hand rotates along the large dial and the minute hand rotates along the small dial. The sum of the time indicated by the minute hand and the second hand is the measured time interval.
Right above the stopwatch is a handle with a button on it. Turn the button and wind up. This is the power of the stopwatch. Use your thumb to control the button, the stopwatch starts to time; press the button again, the stopwatch stops walking and reads; press again, the stopwatch returns to zero, ready for the next time.