| 摘要 |
The housing (1) is closed by a cover, and the outer limiting wall of the channel (2) has a circular cross-section or consists of an equal-sided polygon. In the bottom of the channel may be arranged an inclined ring which presses the ball (3) against the channel outer wall, thus reducing its tendency to move. Specific braking of the ball (3) occurs even when it passes over the angles in the outer wall of the channel (2). Several sensors are evenly distributed along the periphery of the channel, and comprises paired light diodes (5a) and receivers (5b). The ball, in its passage in the channel, breaks the infra-red light beams generated by the light diodes (5a), and this is then recorded by an appropriate registering instrument. The ball is made of soft material e.g. rubber or plastic, enabling it to move as quietly as possible. Electrical sensors may alternatively be used with the ball made of metal, although this creates a noise factor which may be disturb the patients. |
