在使用电磁打点计时器进行实验教学时,有时复写纸片不易自行转动,针头都打在复写纸片的同一点上,打了几点之后,复写纸上该点的油墨就耗尽了,再打出的点就不易辨认出来了。我们对打点计时器的针头进行了改进, In the use of electromagnetic timer for experimental teaching, and sometimes difficult to self-rewrite the paper sheet, the needles are playing in the same point on the carbon paper, after a few hours, the ink on the carbon paper on the exhausted, and then hit the point It is not easy to identify it. We have improved the needle handling timer,