| 摘要 |
A succession of tins (A) to (F) move along a conveyor in the direction of an arrow (10). The tins each cross a beam emitted by a photocell (12). As the tins pass the beam from the photocell (12), the photocell is able to register either that a tin is blocking the beam or that there is no tin blocking the beam. A stream of pulses (14) are continually emitted, the frequency of which is proportional to the speed of the conveyor. When the photocell (12) detects that a tin is present, a counter counts alternate pulses, and the same counter counts every pulse when no tin is sensed. The combined count from the alternate pulses, when a tin is sensed, and each pulse, when a tin is not sensed, is compared with a predetermined value, and if the count is below the predetermined value an indication is given that the tins in their relative position are too close together. |
