手表上的测速仪怎样用？

1.选定一公里路程；
2.在起点处按下按钮A；
3.在终点处再次按下按钮A；
4.读取60秒计时器所指示的表盘外圈的60--400的时速值；就是速度值
5.按下按钮B，计时器归零。

表框Z外边的数字就是用来目测时速的。就是高于60km/h的时速运动时，测量一公里内的速度。从秒针在12点钟开始计时，当走完一公里时观察秒表对应的位置，便可知道当时的时速。例如：秒表停在100的位置，说明当时的时速就是100km/h。

看了这个卡西欧官方网站对计速器（TACHYMETER）的说明，你就知道了。

我简单的说，开启秒表计时，当经过一公里的路程时，秒针所指的那个数字（如120）就是你刚才的时速——120公里每小时。

What is a tachymeter?

The tachymeter is used in the stopwatch mode to measure speed. Two things are needed to be able to judge this. First， the person must be traveling 60 miles or kilometers per hour. Second， there must be a way to judge how far a mile or kilometer is. Mile markers on a highway are a good example.
Start the stopwatch when you pass a mile marker. The seconds hand starts moving， and as it is going around it is pointing at the numbers on the bezel. If you were to pass the next mile marker and stop the stopwatch， the number that is being pointed at would be the speed that you are traveling.