Used to record the displacement time information of moving objects on paper tape, and then quantitatively analyze uniform speed linear motion, measure gravitational acceleration, verify Newton's second law and mechanical energy conservation experiments. A 50 Hz sine alternating current drives the vibrating plate to vibrate up and down in the magnetic field of the permanent magnet steel through a coil; Mark every half cycle (0.02 s) and leave a series of equidistant dots on the paper tape. Magnetic electric structure: coil, vibrating piece, dot nail, magnetic steel, pole shoe, paper tape limit frame, paper pressing frame, carbon paper adjustment piece, terminal post, base and supporting fixture, heavy hammer (300 g).